U.S. patent number 4,084,033 [Application Number 05/693,654] was granted by the patent office on 1978-04-11 for bonded nonwoven fabrics.
This patent grant is currently assigned to Johnson & Johnson. Invention is credited to Arthur H. Drelich.
United States Patent |
4,084,033 |
Drelich |
April 11, 1978 |
Bonded nonwoven fabrics
Abstract
Bonded fibrous nonwoven textile fabrics having excellent
strength and textile-like softness, drape and hand which are
intermittently bonded with synthetic resins in predetermined print
patterns of binder areas having a relatively high, uniform
concentration of from about 50% to about 120% by weight of resin
binder in the binder areas, based on the weight of the fibers
therein, said binder areas having very sharply defined borders or
edges with a minimum of binder feathering thereat whereby the
optical density of the bonded fibrous nonwoven textile fabric very
sharply increases from substantially zero to a maximum of at least
from about 0.6 to about 1.0 or greater in a distance of less than
about 1 mm. (0.04 inch), and methods of depositing such synthetic
resins from colloidal aqueous dispersions thereof onto wet fibrous
webs to form the bonded fibrous nonwoven textile fabrics,
comprising the use of (1) metal complex coordination compounds and
(2) synthetic resins and/or surfactants, at least one of which
contains a specific coordinating ligand capable of being affected
by ions of said metals to control the total migration of the resin
binder during such deposition.
Inventors: |
Drelich; Arthur H. (Plainfield,
NJ) |
Assignee: |
Johnson & Johnson (New
Brunswick, NJ)
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Family
ID: |
24076698 |
Appl.
No.: |
05/693,654 |
Filed: |
June 7, 1976 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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521430 |
Nov 6, 1974 |
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297164 |
Oct 12, 1972 |
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65880 |
Aug 21, 1970 |
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800265 |
Feb 18, 1969 |
3649330 |
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618317 |
Feb 24, 1967 |
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623797 |
Mar 10, 1967 |
3536518 |
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2955 |
Jan 14, 1970 |
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817177 |
Apr 17, 1969 |
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639011 |
May 17, 1967 |
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Current U.S.
Class: |
428/198 |
Current CPC
Class: |
D04H
1/66 (20130101); D04H 1/58 (20130101); Y10T
428/24826 (20150115) |
Current International
Class: |
D04H
1/66 (20060101); D04H 1/64 (20060101); D04H
001/58 (); D04H 001/62 (); D04H 001/66 () |
Field of
Search: |
;428/195,198 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Cannon; J.C.
Attorney, Agent or Firm: Metz; Charles J.
Parent Case Text
This is a continuation-in-part of patent application Ser. No.
521,430, filed Nov. 6, 1974, now abandoned, which is a continuation
of patent application Ser. No. 297,164, filed Oct. 12, 1972, now
abandoned, which is a division of patent application Ser. No.
65,880 filed Aug. 21, 1970 which is a continuation-in-part of my
earlier-filed, co-pending patent application Ser. No. 800,265,
filed Feb. 18, 1969 now U.S. Pat. No. 3,649,330 which is a
continuation-in-part of my earlier-filed patent application Ser.
No. 618,317, filed Feb. 24, 1967, now abandoned. It is also a
continuation-in-part of my earlier-filed, co-pending patent
application Ser. No. 623,797, filed Mar. 10, 1967 now U.S. Pat. No.
3,536,518 and my earlier-filed, co-pending patent application Ser.
No. 2,955, filed Jan. 14, 1970 now abandoned. And, it is also a
continuation-in-part of my earlier-filed, co-pending patent
application Ser. No. 817,177, filed Apr. 17, 1969 which is a
continuation-in-part of my earlier-filed patent application Ser.
No. 639,011, filed May 17, 1967, now abandoned.
Claims
What is claimed is:
1. A bonded, fibrous nonwoven textile fabric having excellent
strength and textile-like softness, drape and hand comprising: a
fibrous web of overlapping, intersecting fibers, said fibrous web
comprising bonded areas and unbonded areas having boundaries
therebetween, said bonded areas being spaced from said unbonded
areas in a predetermined, intermittent pattern; the fibers in said
bonded areas being bonded with from about 50% to about 120% by
weight, based on the weight of the fibers therein, of a synthetic
resin; said boundaries being sharp and distinct and being
substantially free of binder feathering and wherein
(a) the optical density at one side of said bonded areas increases
from approximately 0 to a value of at least 0.6 in moving a
distance of less than about 1 mm. from an unbonded area directly
into a bonded area;
(b) the optical density of said bonded areas is at least 0.6;
and
(c) the optical density at the other side of said bonded areas
decreases to substantially zero in moving a distance of less than
about 1 mm. from said bonded area directly into the next unbonded
area.
2. A bonded, fibrous nonwoven textile fabric as defined in claim 1,
wherein said synthetic resin has a hydroxy-containing coordinating
ligand.
3. A bonded, fibrous nonwoven textile fabric as defined in claim 2,
wherein the hydroxy-containing coordinating ligand is the carboxy
radical.
4. A bonded, fibrous nonwoven textile fabric as defined in claim 2,
wherein said synthetic resin is a carboxylated resin.
5. A bonded, fibrous nonwoven textile fabric as defined in claim 4,
wherein said carboxylated resin is a polymerization product of from
about 1% to about 8% by weight of a .alpha.,.beta.-unsaturated
carboxylic acid and from about 99% to about 92% by weight of a
monomer or mixture of monomers copolymerizable therewith.
6. A bonded, fibrous nonwoven textile fabric as defined in claim 5,
wherein the .alpha.,.beta.-unsaturated carboxylic acid contains
from 3 to 5 carbon atoms.
7. A bonded, fibrous nonwoven textile fabric as defined in claim 5,
wherein the .alpha.,.beta.-unsaturated carboxylic acid is acrylic
acid.
8. A bonded, fibrous nonwoven textile fabric as defined in claim 5,
wherein the .alpha.,.beta.-unsaturated carboxylic acid is
methacrylic acid.
9. A bonded, fibrous nonwoven textile fabric as defined in claim 5,
wherein the .alpha.,.beta.-unsaturated carboxylic acid is itaconic
acid.
10. A bonded, fibrous nonwoven textile fabric as defined in claim
5, wherein the .alpha.,.beta.-unsaturated carboxylic acid is
copolymerized with butadiene and styrene.
11. A bonded, fibrous nonwoven textile fabric as defined in claim
5, wherein the .alpha.,.beta.-unsaturated carboxylic acid is
acrylic acid and the monomer with which it is copolymerized is an
acrylic monomer.
12. A bonded, fibrous nonwoven textile fabric as defined in claim
5, wherein the .alpha.,.beta.-unsaturated caboxylic acid is
copolymerized with ethylene and vinyl acetate.
13. A bonded, fibrous nonwoven textile fabric having excellent
strength and textile-like softness, drape and hand comprising: a
fibrous web of overlapping, intersecting fibers, said fibrous web
comprising bonded areas and unbonded areas having boundaries
therebetween, said bonded areas being spaced from said unbonded
areas in a predetermined, intermittent pattern; the fibers in said
bonded areas being bonded with from about 50% to about 120% by
weight, based on the weight of the fibers therein, of a synthetic
resin; said boundaries being sharp and distinct and being
substantially free of binder feathering; said nonwoven fabric being
characterized by an optical density--distance curve which
graphically displays optical density as a function of distance in
millimeters traversed in moving sequentially:
(a) from a first of said unbonded areas directly into one of said
bonded areas;
(b) across said one of said bonded areas; and
(c) from said one of said bonded areas directly into a next
adjacent unbonded area;
said optical density--distance curve across said bonded area being
generally bell-shaped and having two slopes, each of said slopes
being at least 75.degree..
Description
The present invention relates to porous, absorbent, fibrous sheet
materials and to their methods of manufacture. More particularly,
the present invention is concerned with the so-called bonded,
"nonwoven" textile fabrics, i.e., fabrics produced from textile
fibers without the use of conventional spinning, weaving, knitting
or felting operations. Although not limited thereto, the invention
is of primary importance in connection with nonwoven fabrics
derived from "oriented" or carded fibrous webs composed of
textile-length fibers, the major proportion of which are oriented
predominantly in one direction.
Typical of such fabrics are the so-called "MASSLINN" nonwoven
fabrics, some of which are described in greater particularity in
U.S. Pat. Nos. 2,705,687 and 2,705,688, issued Apr. 5, 1955, to D.
R. Petterson et al. and I. S. Ness et al., respectively.
Another aspect of the present invention is its application to
nonwoven fabrics wherein the textile-length fibers were originally
predominantly oriented in one direction but have been reorganized
and rearranged in predetermined designs and patterns of fabric
openings and fiber bundles. Typical of such latter fabrics are the
so-called "KEYBAK" bundled nonwoven fabrics, some of which are
described in particularity in U.S. Pat. Nos. 2,862,251 and
3,033,721, issued Dec. 2, 1958 and May 8, 1962, respectively, to F.
Kalwaites.
Still another aspect of the present invention is its application to
nonwoven fabrics wherein the textile length fibers are disposed at
random by air-laying techniques and are not predominantly oriented
in any one direction. Typical nonwoven fabrics made by such
procedures are termed "isotropic" nonwoven fabrics and are
described, for example, in U.S. Pat. Nos. 2,676,363 and 2,676.364,
issued Apr. 27, 1954, to C. H. Plummer et al.
And, still another aspect of the present invention is its
application to nonwoven fabrics which comprise textile length
fibers and which are made basically by conventional or modified
aqueous papermaking techniques such as are described in greater
particularity in pending patent application, Ser. No. 4,405, filed
Jan. 20, 1970, now abandoned by P. R. Glor and A. H. Drelich. Such
fabrics are also basically "isotropic" and generally have like
properties in all directions.
The conventional base starting material for the majority of these
nonwoven fabrics is usually a fibrous web comprising any of the
common textile-length fibers, or mixtures thereof, the fibers
varying in average length from approximately one-half inch to about
two and one-half inches. Exemplary of such fibers are the natural
fibers such as cotton and wool and the synthetic or man-made
cellulosic fibers, notably rayon or regenerated cellulose.
Other textile length fibers of a synthetic or man-made origin may
be used in various proportions to replace either partially or
perhaps even entirely the previously-named fibers. Such other
fibers include: polyamide fibers such as nylon 6, nylon 66, nylon
610, etc; polyester fibers such as "Dacron", "Fortrel" and "Kodel";
acrylic fibers such as "Acrilan", "Orlon" and "Creslan"; modacrylic
fibers such as "Verel" and "Dynel"; polyoefinic fibers derived from
polyethylene and polypropylene; cellulose ester fibers such as
"Arnel" and "Acele"; polyvinyl alcohol fibers; etc.
These textile length fibers may be substituted either partially or
entirely by fibers having an average length of less than about
one-half inch and down to about one-quarter inch. These fibers, or
mixtures thereof, are customarily processed through any suitable
textile machinery (e.g., a conventional cotton card, a
"Rando-Webber", a papermaking machine, or other fibrous web
producing apparatus) to form a web or sheet of loosely associated
fibers, weighing from about 100 grains to about 2000 grains per
square yard or even higher.
If desired, even shorter fibers, such as wood pulp fibers or cotton
linters, may be used in varying proportions, even up to 100%, where
such shorter length fibers can be handled and processed by
available apparatus. Such shorter fibers have lengths less than 1/4
inch.
The resulting fibrous web or sheet, regardless of its method of
production, is then subjected to at least one of several types of
bonding operations to anchor the individual fibers together to form
a self-sustaining web. One method is to impregnate the fibrous web
over its entire surface area with various well-known bonding
agents, such as natural or synthetic resins. Such over-all
impregnation produces a nonwoven fabric of good longitudinal and
cross strength, acceptable durability and washability and
satisfactory abrasion resistance. However, the nonwoven fabric
tends to be somewhat stiff and boardlike, possessing more of the
properties and characteristics of paper or board than those of a
woven or knitted textile fabric. Consequently, although such
over-all impregnated nonwoven fabrics are satisfactory for many
uses, they are still basically unsatisfactory as general purpose
textile fabrics.
Another well-known bonding method is to print the fibrous web with
intermittent or continuous straight or wavy lines, or areas of
binder extending generally transversely or diagonally across the
web and additionally, if desired, along the fibrous web. The
resulting nonwoven fabric, as exemplified by a product disclosed in
the Goldman U.S. Pat. No. 2,039,312 and sold under the trademark
"MASSLINN", is far more satisfactory as a textile fabric than
over-all impregnated webs in that the softness, drape and hand of
the resulting nonwoven fabric more nearly approach those of a woven
or knitted textile fabric.
The printing of the resin binder on these nonwoven webs is usually
in the form of relatively narrow lines, or elongated rectangular,
triangular or square areas, or annular, circular, or elliptical
binder areas which are spaced apart a predetermined distance which,
at its maximum, is preferably slightly less than the average fiber
length of the fibers constituting the web. This is based on the
theory that the individual fibers of the fibrous web should be
bound together in as few places as possible.
The nominal surface coverage of such binder lines or areas will
vary widely depending upon the precise properties and
characteristics of softness, drape, hand and strength which are
desired in the final bonded product. In practice, the nominal
surface coverage can be designed so that it falls within the range
of from about 10 percent to about 50 percent of the total surface
of the final product. Within the more commercial aspects of the
present invention, however, nominal surface coverages of from about
15 percent to about 40 percent are preferable.
Such bonding increases the strength of the nonwoven fabric and
retains substantially complete freedom of movement for the
individual fibers whereby the desirable softness, drape and hand
are obtained. This spacing of the binder lines and areas has been
accepted by the industry and it has been deemed necessarily so, if
the stiff and board-like appearance, drape and hand of the over-all
impregnated nonwoven fabrics are to be avoided.
The nonwoven fabrics bonded with such line and area binder patterns
have had the desired softness, drape and hand and have not been
undesirably stiff or board-like. However, such nonwoven fabrics
have also possessed some disadvantages.
For example, the relatively narrow binder lines and relatively
small binder areas of the applicator (usually an engraved print
roll) which are laid down on the fibrous web possesses specified
physical dimensions and inter-spatial relationships as they are
initially laid down. Unfortunately, after the binder is laid down
on the wet fibrous web and before it hardens or becomes fixed in
position, it tends to spread, diffuse or migrate whereby its
physical dimensions are increased and its inter-spatial
relationships decreased. And, at the same time, the binder
concentration in the binder area is lowered and rendered less
uniform by the migration of the binder into adjacent fibrous areas.
One of the results of such migration is to make the surface
coverage of the binder areas increase whereby the effect of the
intermittent bonding approaches the effect of the over-all bonding.
As a result, some of the desired softness, drape and hand are lost
and some of the undesired properties of harshness, stiffness and
boardiness are increased.
Various methods have been proposed to prevent or to at least limit
such spreading, diffusing or migration tendencies of such
intermittent binder techniques.
For example, U.S. Pat. No. 3,009,822, issued Nov. 21, 1961 to A. H.
Drelich et al. discloses the use of a non-migratory regenerated
cellulose viscose binder which is applied in intermittent fashion
to fibrous webs under conditions wherein migration is low and the
concentration of the binder in the binder area is as high as 35% by
weight, based on the weight of the fibers in these binder areas.
Such viscose binder possesses inherently reduced spreading,
diffusing and migrating tendencies, thereby increasing the desired
softness, drape and hand of the resulting nonwoven fabric. This
viscose binder has found acceptance in the industry but the use of
other more versatile binders has always been sought.
Resins, or polymers as they are often referred to herein as
interchangeable terms, are high molecular weight organic compounds
and, as used herein, are of a synthetic or man-made origin. These
synthetic or man-made polymers have a chemical structure which
usually can be represented by a regularly repeating small unit,
referred as a "mer", and are formed usually either by an addition
or a condensation polymerization of one or more monomers. Examples
of addition polymers are the polyvinyl chorides, the polyvinyl
acetates, the polyacrylic resins, the polyolefins, the synthetic
rubbers, etc. Examples of condensation polymers are the
polyurethanes, the polyamides, the polyesters, etc.
Of all the various techniques employed in carrying out
polymerization reactions, emulsion polymerization is one of the
most commonly used. Emulsion polymerized resins, notably polyvinyl
chlorides, polyvinyl acetates, and polyacrylic resins, are widely
used throughout many industries. Such resins are generally produced
by emulsifying the monomers, stabilizing the monomer emulsion by
the use of various surfactant systems, and then polymerizing the
monomers in the emulsified state to form a stabilized resin
polymer. The resin polymer is usually dispersed in an aqueous
medium as discrete particles of colloidal dimensions (1 to 2
microns diameter or smaller) and is generally termed throughout the
industry as a "resin dispersion", or a "resin emulsion" or
"latex".
Generally, however, the average particle size in the resin
dispersion is in the range of about 0.1 micron (or micrometer)
diameter, with individual particles ranging up to 1 to 2 microns in
diameter and occasionally up to as high as about 3 or 5 microns in
size. The particle sizes of such colloidal resin dispersions vary a
great deal, not only from one resin dispersion to another but even
within one resin dispersion itself.
The amount of resin binder solids in the resin colloidal aqueous
dispersion varies from about 1/10% solids by weight up to about 60%
by weight or even higher solids, generally dependent upon the
nature of the monomers used, the nature of the resulting polymer
resin, the surfactant system employed, and the conditions under
which the polymerization was carried out.
These resin colloidal dispersions, or resin emulsions, or latexes,
may be anionic, non-ionic, or even polyionic and stable dispersions
are available at pH's of from about 2.5 to about 10.5.
The amount of resin which is applied to the porous or absorbent
material varies within relatively wide limits, depending upon the
resin itself, the nature and character of the porous or absorbent
materials to which the resins are being applied, its intended use,
etc. A general range of from about 4% by weight up to about 50% by
weight, based on the weight of the porous or absorbent material, is
satisfactory under substantially all uses. Within the more
commercial limits, however, a range of from about 10% to about 30%
by weight, based on the weight of the porous or absorbent material,
is preferred.
Such resins have found use in the coating industries for the
coating of woven fabrics, paper and other materials. The resins are
also used as adhesives for laminating materials or for bonding
fibrous webs. These resins have also found wide use as additives in
the manufacture of paper, the printing industry, the decorative
printing of textiles, and in other industries.
In most instances, the resin is colloidally dispersed in water and,
when applied from the aqueous medium to a wet porous or absorbent
sheet material which contains additional water, is carried by the
water until the water is evaporated or otherwise driven off. If it
is desired to place the resin only on the surface of the wet porous
or absorbent sheet material and not to have the resin penetrate
into the porous or absorbent sheet material, such is usually not
possible inasmuch as diffusion takes place between the aqueous
colloidal rasin and the water in the porous material. In this way
the colloidal resin tends to spread into and throughout the porous
material and does not remain merely on its surface.
Or, if it is desired to deposit the resin in specific intermittent
print pattern, such as is used in bonding nonwoven fabrics, the
aqueous colloid tends to diffuse and to wick along the individual
fibers and to carry the resin beyond the confines of the nominal
intermittent print pattern. As a result, although initially placed
on the nonwoven fabric in a specific intermittent print pattern,
the ultimate pattern goes far beyond that due to the spreading or
migration which takes place due to the diffusion of the water and
the resin, until the water is evaporated or otherwise driven
off.
I have discovered new resin binder compositions containing polymers
colloidally dispersed in aqeuous media and new methods of applying
such resin binder compositions to porous or absorbent fibrous
materials, whereby the resins are applied in a controlled,
relatively non-migrating manner. If it is desired that the resin be
placed only on the surface of the porous or absorbent material, my
compositions and methods will allow this to be done. Furthermore,
if it is desired that the resin be impregnated throughout the
material, from one surface to the other surface, again, my
composition and method will allow this to be done.
In patent application Ser. No. 618,317 and 800,265, filed Feb. 24,
1967 and Feb. 18, 1969, respectively, there are disclosed improved
methods of using emulsion polymerized resins which are so prepared
as to be stable under acid conditions, i.e., an environment with a
pH below 7.
In accordance with the invention disclosed in these patent
applications, the resin dispersion comprises from about 0.1% to
about 60% by weight of emulsion polymerized resin solids and from
about 0.01% to about 10% by weight of the resin solids of a water
soluble metal salt. The metal ion of the salt has a valence of at
least +3 and the metal salt is capable of forming an insoluble
oxide, hydroxide, or hydrated oxide under alkaline conditions.
If such a resin composition is utilized in applying resins to
fibrous materials, the deposition of the resin and its migration or
spreading tendencies on such fibrous materials may be controlled by
applying the acidstable resin dispersion to the fibrous material
while substantially simultaneously raising the pH of the dispersion
to a value greater than 7. For example, if it is desired to apply
the resin merely to the surface of the fibrous material, the pH of
the fibrous material is raised to greater than 7 and the
acid-stable dispersion having a pH less than 7 is applied to the
fibrous materials by spraying techniques or by other methods which
apply the resin dispersion basically only on the surface of the
fibrous materials. Microscopic inspection of the fibrous materials
and the resin which has been sprayed thereon will reveal that the
resin has not penetrated into the fibrous material to any
appreciable degree. This, of course, is due to the fact that the
resin dispersion is stable as long as its pH remains on the acid
side, that is, below 7. However, upon contacting the fibrous
material having a pH greater than 7, the pH of the resin dispersion
is raised to greater than 7, its stability vanishes, and it
figuratively "freezes" in position whereby any migration or
penetration inwardly from the point of initial deposition by the
resin dispersion is instantly stopped.
Further, if the application of the resin employs a conventional
rotogravure process using a conventional engraved-roll wherein a
pattern is impressed and printed on the material, the resin print
pattern will penetrate through the material completely due to the
normal pressure of the print roll and will then coagulate and be
fixed in place with minimal migration or lateral spread.
Microscopic inspection of the material and the resin thereon will
reveal that the resin has penetrated directly and completely
through to the other surface of the material but with controlled
and minimal migration or lateral spread from the point of initial
deposition.
On the other hand, if the fibrous material has or is given a pH of
less than 7 and the resin dispersion which, of course, also has a
pH of less than 7 is applied by a conventional engraved print roll
in a rotogravure process, the acid stable dispersion will retain
its stability after deposition and its tendency to migrate or
spread laterally will continue to exist. Therefore, the fibrous
material and the resin dispersion must be substantially immediately
treated to raise the pH to greater than 7. The resin will then be
deposited through the fibrous material from the top surface to the
bottom in the print patterns of the engraved print roll but the
substantially immediate conversion to a system having a pH greater
than 7 will immediately control migration or lateral side spread
from the point of initial deposition.
The principles of the invention described in these patent
applications also find application in impregnation or "over-all"
bonding processes, wherein a fibrous material is passed into and
through an impregnating bath of the acid-stable resin dispersion.
It has been noted that the resin dispersion which substantially
completely impregnates the fibrous material has a tendency to
migrate to the surfaces thereof, particularly during the drying
process, leaving the center with a lesser concentration of resin
solids, and creating a so-called "soft-center" which is often not
desired. If the over-all bonded and impregnated material is treated
with an alkali to raise the pH to above 7, before the drying step
is initiated, then the impregnating resin dispersion is again
"frozen" in place and there is substantially no tendency of the
resin dispersion to migrate to the surfaces and create a
"soft-center" during the drying operation. Other variations will,
of course, be readily apparent to one skilled in the art.
In the dispersion of the emulsion polymerized, colloidal resin
particles, there exists around each particle, an electrokinetic
charge generally called the Zeta Potential. In most colloids this
charge is negative and tends to cause the particles to repel each
other and hence, stay in the dispersed form. It is believed that
the addition of the salts, as described above, to the colloidal
resin dispersion allows this Zeta Potential to be controlled by
controlling the pH of the dispersion. When the pH of the dispersion
is brought to above about 7 in the presence of the appropriate
metal salt, the Zeta Potential of the colloidal resin particles is
reduced to substantially zero and the individual particles no
longer repel each other. The dispersion becomes unstable and the
deposition of the resin on other substances may be controlled.
This, of course, is only one suspected theory as to why my new
composition allows for controlled resin deposition.
The salts used in accordance with this invention described in these
patent applications are the salts of metals, wherein, the cation
has a positive valence of 3 or higher. Suitable examples of such
metals are zirconium, thorium, aluminum, iron, chromium, etc. The
salt may be sulfate, acetate, nitrate, chloride, etc., or virtually
any salt so long as the metal ion has a positive valence of 3 or
greater. The salt must be capable of forming an insoluble oxide,
hydroxide or hydrated oxide under alkaline conditions.
The amount of salt used will vary in accordance with the resin used
and with the degree of control of the resin deposition that is
desired. From about 0.01% to 10% or even higher by weight of the
amount of resin solids present of metal salt may be used in
accordance with the invention described in these patent
applications. The control at the lower percentages of salt may be
difficult in some instances and it is preferred to keep this lower
limit above about 0.1%. It is uneconomical to use the higher
amounts of salts especially in view of the relative cost of some of
the salts compared to the resin and hence, it is preferred to keep
the upper limit as 2% or less.
The resins which may be used in the method of the present invention
are the emulsion polymerized resins which are in the form of solid
resin particles dispersed in a liquid which is usually water. These
resin dispersions or resin emulsions as they are called, are
stabilized by various types of surfactant systems and the
dispersion is stable under acid conditions. Suitable examples would
be the polyvinyl chlorides, polyvinyl acetates, polyacrylic resins,
etc. Materials such as natural rubber or synthetic rubber are
unsuitable for use in accordance with the invention described in
these patent applications as they have oleates or soaps present
which appear to disrupt the mechanism of the present invention.
The resin emulsion may be anionic or non-ionic or in fact may be
polyionic so long as it is stable under the acid conditions. By
being stable under acid conditions it is meant that the resin
dispersion will remain in the dispersed state at pH's of from 7 or
slightly less than 7 down to the very acid pH's such as 2 or 3.
Generally, the particle size in the resin dispersions will vary
from about 1/10 of a micron or smaller to 3 to 5 microns in size.
And the amount of resin solids in the dispersion will vary from
1/10 of a percent solids up to 60% or even higher solids, generally
dependent upon the resin used, the surfactant system used and the
conditions under which the resin is polymerized.
The salt may be added to the resin dispersion either in its solid
form or it may be initially disssolved in water and the salt
solution added to the resin dispersion.
The resin dispersion is stable as long as the pH is less than 7,
however, once the pH is raised to greater than 7, it appears that
the Zeta Potential of the resin particles is reduced and possibly
brought to zero which causes the resin particles to conglomerate or
coagulate. If the surface of a fibrous web contains an alkali and
the composition of resin and metal salt as previously described is
placed on the web, the particles will immediately be attracted to
the fibers and coagulate on the surface of the fibers.
The pH may be raised by any of the known alkalies such as ammonium
hydroxide, sodium hydroxide, potassium hydroxide, lithium
hydroxide, sodium carbonate or any other material which will give a
pH of greater than 7. The alkali and amount of alkali used is
controlled by economics and by the effect the alkali may have on
the other material, for example, sodium hydroxide can do great
damage to cotton fibers and will interfere with the curing of many
resins. It will be readily apparent to one skilled in the art that
suitable alkalies and concentrations may be chosen dependent on the
material to be treated.
In some instances the resin may contain active cross-linking
co-monomers, such as the acrylic resins having N-methylol
acrylamide or other type groups. When such resins are used in the
presence of certain metal salts, especially zirconium salts, the
zirconium may cross-link and form various complexes with these
resins which in turn improves the binding properties of the resin.
It appears to be immaterial whether the metal salt cross-links or
does not cross-link the resin as far as controlling the deposition
of the resin in accordance with the present invention.
In patent applications Ser. Nos. 623,797 and 2,955, filed Mar. 10,
1967 and Jan. 14, 1970, respectively, there are disclosed other
improved methods of using emulsion polymerized resins which are so
prepared as to be stable under alkaline conditions, i.e., pH's of 7
to 9 or higher.
In accordance with the invention disclosed in these latter two
patent applications, there is utilized a stable emulsion
polymerized resin dispersion having a pH of from about 7 to 9 and
an anionic surfactant selected from the class consisting of alkyl
aromatic sulfonic acids, alkyl sulfonic acid and carboxylic acids.
The dispersion comprises from about 0.1% to 75% by weight of
emulsion polymerized resin solids, from about 0.1% to 5% by weight
of the resin solids of an anionic surfactant selected from the
class consisting of alkyl aromatic sulfonic acids, alkyl sulfonic
acids and carboxylic acids and from about 0.01% to 2% by weight of
the resin solids of a metal chelate compound.
If the resin composition described in these patent applications is
applied to porous materials, its deposition may be controlled by
applying it to the porous material while substantially
simultaneously lowering its pH to a value less than 7. For example,
if it is desired to apply the resin merely to the surface of the
porous material, the pH of the porous material is lowered to less
than 7 and the dispersion, in accordance with the present
invention, then applied to the porous material. The resin will be
deposited substantially only on the surface of the porous material.
On the other hand, if the porous material is given a pH of greater
than 7 and the resin applied and then the porous material
substantially immediately treated to lower its pH to less than 7,
the resin will be deposited throughout the porous material. Other
variations will, of course, be readily apparent to one skilled in
the art.
It is believed that the anionic surfactant in the resin dispersion
system maintains the colloidal dispersion of solid particles in a
stable dispersed form. When a potentially strong cation such as is
present in a chelate compound is introduced in the resin dispersion
and the resin dispersion made acid forming the cation, the cation
destroys the surfactant system precipitating the resin particles
and allowing for control of the deposition of the resin on other
substances. This, of course, is only one suspected theory as to why
my new composition allows for controlled resin deposition.
The metal chelate compounds suitable for use with the invention
disclosed in these patent applications are compounds in which atoms
of the same chelate molecule are coordinated with a metal ion.
Suitable metals in the chelate compound are calcium, magnesium,
iron, zinc, cooper, tin, etc. Suitable chelate compounds are the
metal chelates of ethylenediaminetetraacetic acid, the metal
chelates of salicylaldehyde imine, the metal chelates of condensed
phosphates, the metal chelates of ammonium triacetic acid, etc.
The amount of metal chelate compound used will vary in accordance
with the resin used and with the degree of control of the resin
deposition that is desired. From about 0.01% to 2% or even higher
by weight of the amount of resin solids present of the metal
chelate compound may be used in accordance with the present
invention. It is uneconomical to use the higher amounts of chelates
especially in view of the relative cost of some of the chelates
compared to the resin and hence, it is preferred to keep the upper
limit at 2% or less.
The resins which may be used in the method disclosed in these
patent applications are the emulsion polymerized resins which are
in the form of solid resin particles dispersed in a liquid which is
usually water. These resin dispersions or resin emulsions as they
are called, are stabilized by an anionic surfactant system and the
dispersion is stable at pH's of 7 to 9. Suitable examples are the
polyvinyl chlorides, polyvinyl acetates, polyacrylic resins,
synthetic rubber latexes, etc.
Generally, the particle sizes in the resin dispersions vary from
about 1/10 of a micron or smaller to 3 to 5 microns in size. And
the amount of resin solids in the dispersion varies from 1/10 of a
percent solids up to 60% or even higher solids, generally dependent
upon the resin used, the surfactant system and the conditions under
which the polymerization was carried out.
The surfactant system used must be anionic and the anionic
surfactant must be capable of precipitation by a cation. Suitable
anionic surfactants are the alkyl aromatic sulfonic acids, alkyl
sulfonic acids and the carboxylic acids, such as dodecyl benzene
sulfonate, octyl benzene sulfonate, hexyl benzene sulfonate,
octadecyl benzene sulfonate, cetyl sulfonate, hexyl sulfonate,
dodecyl sulfonate, octadecyl sulfonate, and the sodium and
potassium fatty acid soaps containing from 5 to 18 carbon atoms.
Other anionic surfactants include sodium p-1-methyl alkyl benzene
sulfonates in which the alkyl group contains from 10 to 16 carbon
atoms, the sodium di-n-alkyl sulfosuccinates in which the alkyl
groups contain from 4 to 12 carbon atoms, the potassium n-alkyl
malonates in which the alkyl group contains from 8 to 18 carbon
atoms, the potassium alkyl tricarboxylates in which the alkyl group
contains from 6 to 14 carbon atoms, the alkyl betaines in which the
alkyl group contains from 6 to 14 carbon atoms, the ether alcohol
sulfates, sodium n-alkyl sulfates, containing from 6 to 18 carbon
atoms, etc.
The amount of surfactant used may vary from about 0.1% to 5% by
weight of the resin solids dependent on the type resin being
polymerized and the conditions under which it is polymerized.
The resin dispersion containing the metal chelate compound is
stable as long as the pH is from about 7 to 9. However, once the pH
is lowered below about 7, it appears that the metal cation is
released and attacks the anionic surfactant system in the resin
dispersion causing the resin particles to agglomerate or coagulate.
If the surface of a fibrous web contains a dilute acid and the
composition of resin and metal chelate compound as previously
described is placed on the web, the particles will immediately
coagulate on the surface of the fibers.
The pH may be lowered by any of the known dilute acids such as
acetic acid, or any other material which will give a pH of less
than 7. The dilute acid and amount of acid used is controlled by
economics and by the effect the acid may have on the other
material. It will be readily apparent to one skilled in the art
that suitable acids and concentrations may be chosen dependent on
the material to be treated.
In patent applications Ser. Nos. 639,011 and 817,177, filed May 17,
1967 and Apr. 17, 1969, respectively, there are disclosed still
other improved methods of using emulsion polymerized resins which
are stable under moderately acid or alkaline conditions, i.e., pH's
of from about 2.5 to about 10.5.
In accordance with the invention disclosed in these latter two
patent applications, the deposition of emulsion polymerized resins
on absorbent materials may be controlled by first treating the
absorbent material with an aqueous solution containing from about
0.02% to 1% of a high molecular weight polyelectrolyte polymer
having cationic constituents containing nitrogen in the form of
amines, amine salts, imines, amides, etc., and applying the
emulsion polymerized resin to the treated absorbent material.
Unexpectedly, the diffusion of the resin in the absorbent material
is greatly inhibited even in the presence of large amounts of
water.
In the dispersion of the emulsion polymerized, colloidal resin
particles, there exists around each particle, an electrokinetic
charge called the Zeta Potential. In most colloids this charge is
negative and tends to cause the particles to repel each other and
stay in the dispersed form. It is believed that a polyelectrolyte
polymer containing certain cationic constituents reduces the Zeta
Potential of the resin particles and by so doing inhibits the
particle from diffusing in its water carrier. This, of course, is
one suspected theory as to why my new methods allow for the control
of the deposition of resins on absorbent materials.
The desired binder migration control resulting from the
pretreatment of the absorbent material with the aqueous
polyelectrolyte solution and the subsequent printing of the
impregnated absorbent material with the desired pattern of
polymeric resin binder, however, is realized fully only if the
printing with the polymeric resin binder takes place while the
absorbent material is still wet with the polyelectrolyte solution.
Under such circumstances, the penetration of the polymeric resin
binder into the absorbent material rapidly takes place under
controlled conditions and resin bonding takes place completely
through the absorbent material from the top surface to the bottom
surface substantially instantaneously.
Such a bonded absorbent material with a suitable binder is capable
of withstanding laundering and/or dry cleaning; it withstands
relatively rough usage and has good abrasion resistance.
However, if drying of the absorbent material were permitted
subsequent to the impregnation with the polyelectrolyte solution
and the polymeric resin binder were to be applied to the dried
absorbent material, there would be very little penetration of the
polymeric resin binder into the absorbent material and there would
merely be a surface deposition of polymeric resin binder on the top
surface of the absorbent material. As a result, the absorbent
material, being unbonded on the back side, would not be acceptable
as a uniformly or adequately bonded product, for example, in the
nonwoven fabric industry. It would be incapable of withstanding
laundering; it would fall apart in use; and the unbonded back
surface would be incapable of resisting abrasion.
The polyelectrolyte compounds suitable for use are the high
molecular weight polymers which are water soluble or colloidally
dispersible and have a repeating cationic constituent on the
polymer backbone. The cationic substituents suitable for use in
accordance with the invention are those groups containing nitrogen
having a positive charge as are well known in the art, it includes
the amines, amine salts, imines, amides, etc.
The amount of polyelectrolyte compound used will vary in accordance
with its cationic activity, the resin used and the degree of
control of resin deposition that is desired. From about 0.1% to 5%
of polyelectrolyte by weight of the resin to be deposited on the
absorbent surface may be used in accordance with the invention
disclosed in these patent applications. It is uneconomical to use
the higher amounts of polyelectrolytes especially in view of the
relative cost of some of these compounds compared to the resin and
hence, it is preferred to keep the upper limit at 5% or less.
The resins which may be used in the method of the invention
disclosed in these patent applications are the emulsion polymerized
resins which are in the form of solid resin particles dispersed in
a liquid which is usually water. These resin dispersions or resin
emulsions as they are called, may be anionic, non-ionic or even
polyionic and the dispersion is stable at pH's of 2.5 to 10.5.
Suitable examples are the polyvinyl chlorides, polyvinyl acetates,
polyacrylic resins, etc.
Generally, the particle size in the resin dispersions will vary
from about 1/10 of a micron or smaller to 3 to 5 microns in size.
The amount of resin solids in the dispersion will vary from 1/10 of
a percent solids up to 75% or even higher solids, generally
dependent upon the resin used, the surfactant system and the
conditions under which the polymerization was carried out.
The amount of resin which is applied to the absobent material
varies within relatively wide limits, depending upon the resin
binder itself, the nature and character of the absorbent material
being bonded, its intended use, etc. A range of from about 4% by
weight to about 50% by weight, based on the weight of the absorbent
material, is satisfactory under substantially all uses. Within the
more commercial limits, however, a range of from about 5% by weight
to about 30% by weight, based on the weight of the absorbent
material, is preferred.
In carrying the invention disclosed in these patent applications
into practice, the polyelectrolyte is dissolved or dispersed in an
aqueous medium and the aqueous medium containing the
polyelectrolyte applied to the absorbent material to be treated
with resin. The medium containing the polyelectrolyte may be
sprayed or padded onto the absorbent material as desired. The resin
dispersion is applied to the treated absorbent material by printing
the resin dispersion on the material or by padding, spraying,
impregnating or other techniques for applying emulsion polymerized
resins to absorbent materials.
I have now discovered still another improved method of controllably
depositing colloidal resin compositions on porous or absorbent
materials whereby spreading, diffusing, and migration of the resin
are controlled and are markedly reduced and wherein the
concentration of the resin in the resin binder area reaches
exceptionally high values. When applied to fibrous webs in the
manufacture of nonwoven fabrics, excellent strength is obtained in
the resulting fabrics along with desirable textile-like softness,
hand and drape.
The improved method involves the use of an aqueous resin dispersion
which comprises from about 0.1% to about 60% by weight on a solids
basis of a colloidal resin containing a coordinating ligand, said
resin dispersion being stable at pH's of about 7 and greater but
which is unstable at pH's of below 7 when in the presence of heavy
metal ions such as zirconium, chromium, nickel, cobalt, cadmium,
zinc, vanadium, titanium, copper and aluminum.
The coordinating ligand is normally an acidic or proton donor
group, especially those containing terminal hydroxy groups.
Examples of hydroxy-containing coordinating ligands are: hydroxy
--OH; carboxy --COOH; sulfino --SO(OH); sulfo --SO.sub.2 (OH);
sulfonoamino --NHSO.sub.2 (OH); aci-nitro.dbd.NO(OH); hydroxyamino
--NHOH; hydroxyimino .dbd. NOH; etc. It is to be observed that
these hydroxy-containing radicals contain a hydrogen atom which is
capable of dissociating to form an H.sup.+ ion or proton.
The colloidal resins possessing a hydroxy-containing coordinating
ligand are obtained by copolymerizing from about 92% by weight to
about 99% by weight of a monomer or a mixture of monomers of the
group comprising vinyl halide, vinyl ester, or vinyl ether monomers
including, for example, vinyl chloride, vinyl acetate and vinyl
ethyl ether; olefins such as ethylene and propylene; acrylic and
methacrylic monomers including, for example, ethyl acrylate, ethyl
hexyl acrylate, methyl acrylate, propyl acrylate, butyl acrylate,
hydroxyethyl acrylate, dimethyl amino ethyl acrylate, methyl
methacrylate, ethyl methacrylate, isopropyl methacrylate, butyl
methacrylate, acrylonitrile, methacrylonitrile, acrylamide,
N-isopropyl acrylamide, N-methylol acrylamide, methacrylamide;
vinylidene monomers such as vinylidene chloride; diene monomers
including, for example, 1,2-butadiene, 1,3-butadiene,
2-ethyl-1,3-butadiene; styrene monomers including, for example,
styrene, 2-methyl styrene, 3-methyl styrene, 4-methyl styrene,
4-ethyl styrene, 4-butyl styrene; and other polymerizable monomers,
with a relatively small amount, on the order of from about 1% by
weight to about 8% by weight of an unsaturated acid containing a
terminal hydroxy group such as the .alpha.,.beta.-unsaturated
carboxylic acids including acrylic acid, methacrylic acid, fumaric
acid, maleic acid, itaconic acid, crotonic acid, isocrotonic acid,
angelic acid, tiglic acid, etc. Anhydrides which exist of these
acids are also of use. Other .alpha.,.beta.-unsaturated acids are
of use and include 2-sulfoethyl methacrylate, styrene sulfonic
acid, vinyl phosphonic acid, etc.
It is to be appreciated that more than one monomer may be included
in the polymerization with the .alpha.,.beta.-unsaturated acid
containing a terminal hydroxy group. An outstanding example of the
use of more than one monomer is the polymerization of butadiene and
styrene with an .alpha.,.beta.-unsaturated acid such as acrylic
acid, methacrylic acid, fumaric acid, maleic acid, or itaconic
acid. Anhydrides, for example, maleic anhydride, are also of
use.
To the resulting emulsion polymerized composition containing the
colloidal resin with its coordinating ligand is added a small
amount of from about 0.1% by weight to about 3% by weight, based on
the weight of the synthetic resin solids, of a coordination metal
complex compound wherein the central metallic atom is zirconium,
chromium, nickel, cobalt, cadmium, zinc, vanadium, titanium, copper
or aluminum.
Examples of such coordination compounds are:
ammonium carbonato zirconate
sodium tetraoxalato zirconate
ammonium heptafluoro zirconate
ammonium tetrathiocyanato diammine chromate
sodium pentacarbonyl chromate
hexammine chromium chloride
hexa urea chromium fluosilicate
chloro pentammine chromium chloride
hexammine nickel chloride
sodium tetracyano nickelate
hexammine nickel bromide
hexammine nickel chlorate
hexammine nickel iodide
hexammine nickel nitrate
tetra pyridine nickel fluosilicate
tetrammine zinc carbonate
tetrammine zinc sulfate
potassium tetracyano zincate
sodium tetrahydroxo zincate
diammine zinc chloride
tetrapyridine zinc fluosilicate
sodium tetrahydroxo aluminate
potassium trioxalato aluminate
tetrapyridine cadmium fluosilicate
hexammine cobalt chloride
hexammine cobalt iodide
hexammine cobalt nitrate
hexammine cobalt sulfate
hexammine cobalt bromide
dinitro tetrammine cobalt nitrate
diammine copper acetate
tetrammine copper sulfate
tetrapyridine copper fluosilicate
as defined herein, a metal complex coordination compound is one of
a number of types of metal complex compounds, usually made by
addition of organic or inorganic atoms or groups to simple
inorganic compounds containing the metal atom. Coordination
compounds are therefore essentially compounds to which atoms or
groups are added beyond the number possible of explanation on the
basis of electrovalent linkages, or the usual covalent linkages,
wherein each of the two atoms linked donate one electron to form
the duplet. In the cases of the coordination compounds, the
coordinated atoms or groups are linked to the atoms of the
coordination compound, usually by coordinate valences, in which
both the electrons in the bond are furnished by the linked atoms of
the coordinated group.
The emulsion polymerized, ligand-containing resin and the
coordination compound exist together in a stable emulsion form and
normally do not agglomerate, coagulate or precipitate, as long as
the pH remains at about 7 or above. Ammonia, alkali hydroxides and
carbonates, or other alkaline compounds may be used in order to
insure such neutral or alkaline pH range. In some cases, excess
NH.sub.4 OH must be present in the mixture for stability.
Subsequently, when the emulsion is acidified to an acid pH below 7,
the resin immediately coagulates and agglomerates in place with
substantially no further spreading, diffusion or migration.
It is believed that, when the pH is reduced to below 7, the metal
cation is released from the coordination compound and immediately
attacks or reacts with the ligand-containing resin causing the
resin particles to agglomerate or coagulate.
It is also to be appreciated that, when the pH is reduced to below
7, the metal cation which is released from the coordination
compound also is capable of attacking or reacting with any other
chemical compounds which are present and which possess anionic
groups, particularly those containing terminal hydroxy groups such
as hydroxy, carboxy, sulfino, sulfo, and like acid groups.
For example, the metal cation which is released immediately attacks
a surfactant system which is anionic and contains surfactants such
as alkyl aromatic sulfonic acids, alkyl sulfonic acids, the
carboxylic acids, and other anionic surfactants described
hereinbefore and in greater particularity in patent applications
Ser. Nos. 623,797 and 2,955. Such anionic surfactants are present
in the colloidal dispersion in amounts of from about 0.01% to about
2% by weight, based on the weight of the synthetic resin
solids.
The specific surfactant which is selected for use in the resin
composition does not relate to the essence of the invention. It is
merely necessary that it possess the necessary properties and
characteristics to carry out its indicated function of stabilizing
the resin composition prior to the time that coagulation and
precipitation of the resin is required. Additionally, in the event
that it is desired that the surfactant assist in or promote the
coagulation and precipitation function, then it must possess the
necessary anionic groups, as described hereinbefore, which are
capable of reaction due to the presence of the metal cations
released from the metal complex coordination compound.
The mechanism of instant controlled agglomeration, coagulation and
precipitation of the colloidal resin binder may therefore be
triggered by reaction of the metal cation which is released and
reacts with either the colloidal resin, or the anionic surfactant,
or both.
The pH may be lowered in different ways in order to activate the
reaction mechanism. For example, the porous or absorbent fibrous
material may be pre-treated by being pre-wet with a sufficient
quantity of an acidic material such as acetic acid, whereby the
alkaline colloidal resin composition immediately becomes acid upon
contact therewith. Or, if desired, the alkaline colloidal resin
composition may be first printed on the alkaline or neutral porous
or absorbent fibrous material and then substantially immediately
treated with the acidic material, such as acetic acid, to reduce
the pH to below 7 whereupon the colloidal resin particles
substantially immediately controllably agglomerate or coagulate in
place with no further spreading, diffusion or migration.
The acid which is used to acidify the colloidal resin composition
is preferably a weak acid such as acetic acid, citric acid,
phosphoric acid, lactic acid, tartaric acid, oxalic acid, etc., or
an acid salt such as alum.
The pH may be lowered in other ways in order to activate the
reaction mechanism. For example, in a case wherein the pH is
created or affected by the presence of a volatile material such as
ammonia, for example, heating to expel the volatile material will
bring about the desired change in pH to activate the reaction
mechanism.
When printed on a fibrous web during the manufacture of nonwoven
fabrics, the controlled total migration of the resin binder solids
may be reduced to as little as about 50% beyond the originally
deposited area. In some instances, the migration is relatively
negligible. Normally, however, the total controlled migrational
increase in area of the resin binder solids, even under the most
adverse conditions does not materially exceed about 200%. Such
values are to be compared to increases in binder migration of at
least about 300% and up to about 800% when emulsion polymerized
resins are applied to fibrous porous absorbent sheet materials,
unaided by the principles referred to or disclosed herein.
The concentration of the binder resin solids in the binder area is
correspondingly increased and is in the range of from about 50% by
weight to about 120% by weight, and more normally about 60% to
about 80% by weight, based on the weight of the fibers in the
binder area.
The excellent migration control exercised over the resin binder is
illustrated in the drawings in which:
FIG. 1 is an enlarged, idealized cross-sectional view of a bonded
nonwoven fabric illustrating the principles of the present
invention;
FIG. 2 is an enlarged, idealized cross-sectional view of a bonded
nonwoven fabric, not utilizing the principles of the present
invention;
FIG. 3A is a further enlarged, idealized cross-sectional view of
the nonwoven fabrics of FIGS. 1 and 2, taken on the line 3--3
thereof, before any resin binder has been applied to the fibrous
web;
FIG. 3B is a further enlarged, idealized cross-sectional view of
the nonwoven fabrics of FIGS. 1 and 2, taken on the line 3--3
thereof, at the moment the resin binder is applied to the fibrous
web; it is also an enlarged, idealized cross-sectional view of the
invention nonwoven fabric of FIG. 1, taken on the line 3--3
thereof, after the resin binder has set;
FIG. 3C is a further enlarged idealized, cross-sectional view of
the fibrous web of FIG. 2 taken on the line 3--3 thereof, after the
resin binder has set;
FIG. 4A is a further enlarged, idealized cross-sectional view of
the nonwoven fabrics of FIGS. 1 and 2, taken on the line 4--4
thereof, before any resin binder has been applied to the fibrous
web;
FIG. 4B is a further enlarged, idealized cross-sectional view of
the nonwoven fabrics of FIGS. 1 and 2, taken on the line 4--4
thereof, at the moment the resin binder is applied to the fibrous
web; it is also an enlarged idealized cross-sectional view of the
invention nonwoven fabric of FIG. 1, taken on the line 4--4
thereof, after the resin binder has set;
FIG. 4C is a further enlarged, idealized cross-sectional view of
the nonwoven fabric of FIG. 2, taken on the line 4--4 thereof,
after the resin binder has set;
FIG. 5A is an idealized graph or histogram showing the surface
coverage and the concentration of an ideal binder on a nonwoven
fabric;
FIG. 5B is a graph or histogram showing the surface coverage and
the concentration of a binder placed on a nonwoven fabric in
accordance with the principles of the present invention;
FIG. 5C is a graph or histogram showing the surface coverage and
the concentration of a binder placed on a nonwoven fabric but not
in accordance with the principles of the present invention;
FIG. 6 shows a graph or histogram of the critical bonded areas of
FIGS. 5A, 5B, and 5C in superimposed fashion to accentuate their
differences and similarities;
FIG. 7 is a pair of superimposed graphs or histograms of the binder
concentrations on nonwoven fabrics showing their differences.
FIG. 8 is another graph or histogram of a binder deposition of a
nonwoven fabric showing surface coverage and concentration of
binder in the binder area;
FIG. 9 is another graph or histogram of a binder deposition on a
nonwoven fabric showing the surface coverage and concentration of
binder in the binder area; and
FIG. 10 is still another graph or histogram of a binder deposition
on a nonwoven fabric showing the surface coverage and concentration
of binder in the binder area.
With reference to the drawings and with particular reference to
FIG. 1 thereof, there is shown a bonded nonwoven fabric 10 which
has been bonded according to the principles of the present
invention. The bonded nonwoven fabric 10 comprises fibrous areas 12
of unbonded overlapping, intersecting fibers 14 and bonded areas 16
containing bonded fibers 18 and a resin binder 19. As shown, the
bonded areas 16 extend completely through the bonded nonwoven
fabric 10 from one surface to the other surface and possesses
relatively straight, sharp, distinct edges or boundary lines, 16a
and 16b.
The sharpness and distinctness of the edges or boundary lines which
exist between the bonded areas 16 and the unbonded areas 12 is
attested to by the fact that the optical density of the bonded
nonwoven fabric 10 increases from about 0.0 optical density to as
much as from about 0.6 to about 1.0 optical density in merely
moving a distance of about 1 mm. (0.04 inch) or less, lengthwise of
the nonwoven fabric from the unbonded area into the bonded area.
The uniformity of the binder concentration in the bonded areas 16
of nonwoven fabric 10 is attested to by the fact that, after the
optical density increases from about 0.0 to about 0.6 or more in
moving a distance of about 1 mm from an unbonded area into a bonded
area, the optical density remains at about 0.6 or higher in moving
through the bonded area toward the next unbonded area of the
fabric. The optical density thereafter decreases from its value of
about 0.6 or higher to a value of about 0.0 in merely moving a
distance of about 1 mm from the uniformly bonded area toward the
next unbonded area. Thus it will be recognized that sides 16a, 16b
of the bonded areas, which sides correspond to the boundaries
between the bonded and unbonded areas of the fabric, are relatively
straight, sharp, and distinct. This feature will be described in
greater detail hereinafter.
As defined herein, optical density varies generally proportionately
to the concentration of binder and is equal to the logarithm (base
10) of the ratio of (1) the intensity of an incident ray (I.sub.i)
falling upon a transparent or a translucent medium to (2) the
intensity of a transmitted ray (I.sub.t) which passes through the
transparent or translucent medium. This quantity (log.sub.10
I.sub.i /I.sub.t) is therefore a measure of the degree of ability
of light to pass through the medium. When the fibers are made
transparent and the binder is made opaque, the optical density is a
measure of the intensity or the concentration of the binder on the
nonwoven fabric. Since it is frequently not possible to make the
fibers transparent, an alternate procedure, based on differential
staining of fiber and binder, measuring light reflectance may also
be used.
Inasmuch as the optical density is a logarithmic function and
difficult to compare directly, optical transparency will also be
used in this description of the invention. As defined herein,
optical transparency is equal to I.sub.t /I.sub.i, or it is the
direct ratio of the intensity of the transmitted light (I.sub.t) to
the intensity of the incident light (I.sub.i). Such a term is more
easily employed for direct comparison purposes.
It is important to describe the procedures which are used for
determining (1) the sharpness and the distinctness of the boundary
lines which exist between the bonded areas and the unbonded areas;
(2) the border or edge feathering and total surface coverage of the
binder; (3) the optical densities and transparencies of various
points in the bonded areas; (4) the concentration of the binder in
the bonded areas; (5) the uniformity of the binder concentration in
the bonded areas; etc.
It has long been known that the actual width of a bond on a
nonwoven fabric is greater than the nominal width of the engraved
line on the print roll which applied the binder to the fibrous web
during the making of a bonded nonwoven fabric. The difference
between the two widths is, of course, the binder migration.
It is relatively easy to measure the nominal width of the engraved
line on the print roll. However, a problem has always existed as to
the best method for accurately measuring the actual bond width on
the bonded nonwoven fabric. Incorporating a dye or pigment in a
resin binder and measuring the resultant colored binder area is
misleading. It is now known that the binder spreads much farther in
the fibrous web than the pigment or dye because of a
chromatographic phenomenon among the fibers. As a result, a
subjective viewing of a resin bonded nonwoven fabric will merely
reveal the width of the pigmented or dyed area which is
considerably less than that of the bonded area covered by the
binder.
Incorporating a pigment or dye in a viscose binder, as compared to
a resin binder, and measuring the resulting colored binder area may
also be misleading, although it is believed that in the case of
bonding with viscose, as differentiated from bonding with a resin
binder, the binder stays more closely with the pigment or dye. In
any event, however, the pigmented or dyed areas are probably less
than the bonded fabric areas which are covered with a viscose
binder.
In the case of practically all the resins used for binder purposes,
differential staining techniques may be employed so that the rayon
fibers are unstained and remain practically white while the resin
binder becomes stained and taken on an intense color. Under
magnification, the colored resin binder is discernible and
distinguishable from the rayon fibers. Such differentially stained
nonwoven fabrics have then been studied under relatively low power
microscopes and the width of the actual binder line has been
subjectively estimated by comparison to a standard scale, usually
in the microscope eyepiece. The binder edge, especially in the case
of a migrated print line, gradually fades to zero or substantially
zero, and the visual estimation of the binder width is therefore a
difficult, subjective procedure. It is now known that prior efforts
to estimate binders widths have led to low estimates inasmuch as
the extremes of the binder-feathering have been neglected.
The improvements brought about by the present invention are
determined by measuring actual bond widths and relative binder
content across a bond stripe by an objective method using an
analytical instrument for the actual measurements. These improved
methods will be described in greater detail hereinafter.
It has been observed that it is characteristic of migrated print
bonded patterns to show a binder-feathering near the bond edges. On
the other hand, when migration is controlled, binder-feathering is
nonexistent and the line of demarcation between bonded area and
non-bonded area is sharp. The feathering, however, in a migrated
binder reflects the diffusion of binder into the water of the wet
web and also the capillary absorption of liquid binder by the web
structure. In contrast, when binder has been coagulated to control
migration, diffusion, capillarity and feathering near the edge of
the bond are essentially nonexistent.
An unusual feature of the feathering phenomenon is the fact that it
is more pronounced on one side of the bonded area. It is believed
that this is caused by the fact that the binder, as it is applied
by an engraved print roll, tends to smear and migrate more on the
trailing side of the applied binder. The leading edge, that is, the
edge first contacted by the print roll, is usually cleaner with
less smearing and less migration.
When binder migration is controlled, the total amount of binder
applied may be selected to be the same but the binder is restricted
to a smaller area within the web. Hence, binder concentration
within the bond area is higher and the line of demarcation between
bond and free-fiber areas is much sharper in controlled nonwoven
fabrics. In fact, it is believed that the feathered edge of the
bond area deleteriously affects nonwoven properties for the
following reasons:
1. The low binder content in the feathered areas is sufficient to
cause stiffness, but not sufficient to impart good strength.
2. The highest concentration of binder attainable in the bond area
in non-controlled print areas is not sufficient to make bonds as
strong as the fibers. On the other hand, when binder migration is
controlled, the binder content is high enough to equal fiber
strengths, but not so high that the bond feels nubby. Furthermore,
the high concentration of binder in the bonded areas in a
controlled printed fabric approaches (but does not reach) a
continuous binder film. Therefore, a better carry-through of binder
properties in the web is obtained, especially strength and
resilience.
Several new concepts, and unexpected results are believed to be
embodied in the controlled migration fabrics which have been made.
A laboratory method for giving numerical values to the fiber-bond
transition area has been developed, based on the staining
properties of binder, and the optical characteristics of a stained
bond area. By this method, the nonwoven fabric is stained with the
proper dye or chemical reagent and the reflected light from the
surface of the various areas of the fabric is measured. The
intensity of staining across a bond is measured by means of its
magnified image on the ground glass of a camera. The microscope
image of the surface of the stained fabric on the camera ground
glass is scanned with a light sensing instrument and a graph of the
intensity of reflected light (as "Optical Density") versus location
across a bond is made.
In order for this procedure to be quantitative and reproducible, it
is necessary to specify many of the details, as follows. The
print-bonded nonwoven fabric is differentially stained in a 1%
solution of Celliton Fast Violet 6BA (manufactured by General
Aniline and Film), by immersion for one minute in boiling solution
and rinsing in cool water until the cellulosic fibers become white.
This dye will stain all of the common types of binders including
acrylics, vinyl acetates, butadienestyrene rubbers, vinyl chloride
polymers, etc. Other dyes may be used as long as the base fibers
are essentially undyed, and the resin itself is dyed an intense
color. The fabrics are air-dried and mounted on a flat white
surface. The mounted sample is placed on a graduated mechanical
stage under a ground glass camera using lenses and distances to
enlarge the image 20.0X by methods well known in the photographic
and microscopic arts. This specimen is illuminated by two small
spot lights mounted at about 45.degree. above the specimen and at
180.degree. from each other, that is, opposite each other in a
straight line.
The probe of an optical densitometer is fixed at the focusing plane
(the ground glass) of the camera. It is convenient to use a reflex
housing so that the specimen can be examined visually or the
reflected image can be measured simply by turning a mirror to
deflect the light for observation or for measurement, respectively.
The size of the probe is set at a 4.times.4 millimeter square.
The two lights illuminating the specimen are carefully placed to
minimize the formation of shadows. An area of the test specimen
which is completely free of binder is moved underneath the sensing
area, and by means of the controls on the densitometer, the needle
reading is set at "0" Optical Density.
The stage micrometer is manipulated to move the specimen in
definite intervals of 0.1 mm., only along the axis perpendicular to
the bond line. As the magnified image is traversed stepwise across
the probe, light reflectivity readings are taken. Light
reflectivity is measured as "Optical Density". As mentioned above,
the actual size of the light sensing probe is 4.times.4 millimeters
and is fixed to the screen where a 20.0X magnified image is
projected. At an actual movement of 0.1 millimeter, the apparent
movement is magnified to 2.0 millimeters at 20X magnification,
hence, the probe of 4.times.4 mm. dimension reads an overlapping
area with each consecutive reading. The purpose of choosing this
probe size and obtaining overlap is to tend towards smoothing the
curve. Otherwise, an erratic reading is obtained.
In other words, the differentially stained test sample, under
constant illumination, is traversed across the field while a fixed
light-sensing probe measures the light reflectance of its magnified
image, hence, the comparative binder content across a single bond
unit.
The intensity of the reflected light, in units of "Optical Density"
yields a comparative measure of binder content across a binder
pattern unit.
This procedure can be used on any nonwoven fabric so long as the
rayon fibers or other fibers are white and are not colored
significantly by the dye which stains the binder.
Such procedures establish that:
1. The binder content within the binder area is higher in
controlled migration samples, and is in the range of about 50%-120%
binder content (based on fiber weight in the same area).
2. The binder penetrates essentially throughout the entire
thickness of the web. This is in sharp contrast to the products of
dry printing where the binder stays on one side of the web.
3. The binder content across the binder area is more uniform in the
controlled sample, that is, there is a virtual absence of
feathering and practically no transition area between clean fiber
and bond area.
Inasmuch as it can be arranged that the total amount of binder
material in each bond unit of a controlled and an uncontrolled
migrational sample of a nonwoven fabric is the same, as determined
by chemical analysis, the areas under the curves in the histograms
of these samples will denote the same amount of binder. However, as
an artifact of the test procedures, based on the saturation color
of the binder stain, the raw data taken by the hereindescribed
procedures usually shows an apparently appreciable higher area
under the curve for the migrated samples.
Hence, it is therefore necessary that the raw data be normalized by
multiplying it by a factor less than one to bring the area under
its curve to that of the controlled migration binder area. In this
way, the controlled and uncontrolled migration bond areas can be
examined and compared. This normalization has been done for FIGS. 7
through 10, but further refinement thereof may be necessary in some
cases.
It is to be appreciated that regardless of whether raw data or
normalized data is used, the zero points and the distances required
to go from zero binder content to maximum binder content or to go
from zero to maximum Optical Density are unchanged. On the other
hand, however, the slopes of the curves and the apparent peak
optical densities are changed.
In FIG. 2, there is illustrated another bonded nonwoven fabric 20
which has not been bonded according to the principles of the
present invention. The bonded nonwoven fabric 20 comprises fibrous
areas 22 of unbonded overlapping, intersecting fibers 24 and bonded
areas 26 containing bonded fibers 28 and a resin binder 29. It is
to be observed that the bonded areas 26, although they were as
small as the bonded areas 16 of FIG. 1, when originally applied to
the fibrous web, are very much larger in the finished fabric and
have much greater actual surface coverage. Also, it is to be noted
that the boundary lines of the binder areas are not relatively
straight, nor are they sharp and distinct, and that the resin
binder is concentrated in the center and feathers and gradually
thins out as the binder edges are approached.
The lack of sharpness or distinctness of the boundary lines which
exist between the bonded areas 26 and the unbonded areas 22 is
attested to by the fact that the optical density of the bonded
nonwoven fabric 20 increases from about 0.0 to only about 0.35 and
that such is accomplished in moving a much greater distance of two
or three millimeters lengthwise of the nonwoven fabric from the
unbonded area into the bonded area.
In other words, the present invention provides for greater
increases of intensity or concentrations of binder in shorter
lengthwise distances of the bonded nonwoven fabric. As a result,
the concentration of the binder in the binder areas is much greater
which is, of course, very desirable. Also, the surface coverage of
the bonded nonwoven fabrics by the binders of the present invention
is very much decreased whereby strength and softness
characteristics and properties are greatly improved.
FIG. 3A is an enlarged, idealized cross-sectional view of the
fibers of the fibrous webs 10 and 20 before any resin binder has
been applied thereto. These fibers are, of course, as yet unbonded.
FIG. 3B is an enlarged, idealized cross-sectional view of the
fibers of the fibrous webs 10 and 20 at the precise moment that the
resin binder is applied thereto and before it has an opportunity to
spread, migrate or diffuse. The resin dispersion is illustrated as
droplets added to the water already present in the pre-wet fibrous
web.
Application of the principles of the present invention causes the
colloidally dispersed resin to agglomerate, coagulate and
precipitate instantly whereby they exist in the final bonded
nonwoven fabric substantially as shown in FIG. 3B.
In FIG. 3C, however, there is illustrated the effect of the
migration, diffusion and spreading of the resin binder which takes
place in the absence of instantaneous agglomeration, coagulation
and precipitation after the binder is deposited on the fibrous web
and before it has time to harden or set. It is to be observed that
the resin binder has shifted to a position within a group of fibers
and does not completely surround many fibers. The changes that have
taken place in the transition from FIG. 3B to FIG. 3C are worthy of
note.
FIG. 4A is an enlarged, idealized cross-sectional view of the
fibers of the fibrous web 10 and 12 before any resin binder has
been applied thereto. These fibers are, of course, as yet unbonded.
FIG. 4B is an enlarged, idealized cross-sectional view of the
fibrous webs 10 and 20 at the precise moment that the resin binder
is applied thereto and before it has an opportunity to spread,
diffuse or migrate. The resin is illustrated as droplets added to
the water already present in the pre-wet fibrous web.
Application of the principles of the present invention causes the
colloidally dispersed resin to agglomerate, coagulate and
precipitate instantly whereby they exist in the final bonded
nonwoven fabric substantially as shown in FIG. 4B.
In FIG. 4C, however, there is illustrated the effect of the
migration, diffusion and spreading of the resin binder which takes
place in the absence of instantaneous agglomeration, coagulation
and precipitation after the binder is deposited on the fibrous web
and before it has time to harden or set. It is to be observed that
the resin binder has shifted to a position within a group of fibers
and does not completely surround many fibers. The changes that have
taken place in the transition from FIG. 4B to FIG. 4C are worthy of
note.
One very important feature of the present invention, as mentioned
previously, is the sharpness and definiteness of the edges or
boundaries of the binder areas. In FIG. 5A, there is illustrated a
graph or histogram depicting the change in the concentration of the
binder in the bonded fabric as measurements are taken,
progressively lengthwise thereof, passing through bonded areas and
non-bonded areas. The ideal situation (FIG. 5A) shows no binder
whatsoever in the unbonded area and a steep 90.degree. rise at the
beginning of the binder area to a maximum flat plateau of high
optical density and high uniform binder concentration in the bonded
area, followed by a steep 90.degree. drop to zero binder
concentration and zero "Optical Density" at the end of the bonded
area. Such 90.degree. slopes are, of course, ideal.
The variation in the concentration of the binder content with
respect to the bonded fabric in the case of the present invention
is shown in FIG. 5B. The slopes of the leading and trailing edges
or boundaries of the binder areas are very close to 90.degree. and
are in the range of from about 75.degree. to about 90.degree.. As a
result of such steep slopes, the maximum flat plateau is
practically at the same level or very slightly lower than the
maximum flat plateau of the ideal binder concentration as that set
forth in FIG. 5A.
On the other hand, when the principles of the present invention are
not followed, the slopes of the leading and trailing edges of the
binder areas fall to a much lower range and are in the range of
from about 30.degree. to about 55.degree.. This is shown in FIG.
5C. As a result, the maximum flat plateau falls considerably and is
in the range of from only about 30% to about 55% of the maximum
flat plateau of the ideal set forth in FIG. 5A.
Another very important feature of the present invention is the
ability to control or confine the total coverage of the binder
areas on the bonded fabric. This is shown in FIG. 6 wherein the
curves or histograms of three typical binder areas are
superimposed. The solid line shows the ideal binder area with
90.degree. slopes, maximum binder concentration in the binder area
and minimum nonwoven fabric coverage. The dash line shows the
present invention binder with slopes of about 85.degree. and a flat
plateau of about 92% of the ideal binder concentration. The
dot-dash line shows binder applied not utilizing the present
invention. The slopes are only about 45.degree. and the flat
plateau is only about 50% of the ideal binder concentration.
The migration of the ideal binder is 0%; the controlled total
migration of the invention binder is less than about 200%, based on
the ideal binder area, whereas the migration of non-invention
binder is in excess of about 300% and up to about 800% based on the
ideal binder area, all of such values including feathered
areas.
FIG. 7 discloses graphs or histograms actually prepared from two
samples of bonded nonwoven fabrics; one utilizing the principles of
the present invention and the other not utilizing the principles of
the present invention.
The average maximum level of the concentration of binder of the
invention fabric has a relatively high peak relative Optical
Density value of about 0.64 with a realtively low peak relative
optical transparency value of about 0.23. These values are reached
in less than 0.7 mm. (0.028 inch). The average level of the
concentration of binder of the non-invention fabric has a
relatively low peak relative Optical Density value of only about
0.35 with a relatively high peak relative optical transparency
value of about 0.45. These values are reached in more than 1.6 mm.
(0.064 inch).
The slopes of the invention binder curves are approximately
84.degree. and 86.degree. whereas the slopes of non-invention
binder curves are approximately only 45.degree. and 49.degree.. The
effective base of both binder areas, as originally laid down, is
approximately 0.024 inch in width. The effective base of the
invention binder curve in the final product is approximately 0.056
inch in width which equals a controlled total migration of 133%.
The effective base of the non-invention binder in the final product
is approximately 0.159 inch in width which equals a migration of
over 560% due primarily to the large amount of feathering.
The same amount of binder is applied in both samples and the areas
under each curve are the same. For a percentage add-on of binder of
24% applied in a six (0.024 inch) horizontal wavy line print
pattern, this equals (for the invention binder) a surface coverage
of 33.6% and a concentration of binder of 72% in the invention
binder area. For the non-invention binder, the surface coverage is
95.4% and the average concentration of binder in the binder area is
only 25.2% due to loss of binder which migrates into the feathered
areas.
The invention binder fabric is strong and has textile-like
softness, drape and hand. The other binder fabric is stiff and
boardy.
The invention will be further illustrated in greater detail by the
following specific examples. It should be understood, however, that
although these examples may describe in particular detail some of
the more specific features of the invention, they are given
primarily for purposes of illustration and the invention in its
broader aspects is not to be construed as limited thereto.
EXAMPLE I
A pad of woodpulp fibers is sprayed with a dilute ammonium
hydroxide solution containing about 5% ammonia. A resin emulsion
containing about 20% acrylic polymer solids, 1% by weight of the
solids of zirconium sulfate, and a blue pigment is sprayed on the
wood pulp pad. The resin emulsion has a pH of about 3. The pad is
dried and examined. By observation the blue color indicates the
resin is in the form of spherical particles on the outside fiber
layer of the pad. The pad is soft yet has sufficient strength and
absorbency to be useful as a sanitary pad. The above experiment is
repeated with the exception that the zirconium sulfate is omitted.
The resultant pad has a film of resin which has penetrated the
woodpulp pad rendering the pad stiff, water repellent and
unsuitable for use as a sanitary pad.
EXAMPLE II
A web of 100% rayon fibers, 11/2 denier and 11/2 inch in length is
print-bonded by the rotogravure process using an engraved roll
having 6 horizontal wavy lines per inch. The width of each line is
about 0.018 inch. The composition of the resin used for the
print-bonding is:
______________________________________ Self cross-linking acrylic
polymer, predominantly polyethyl acrylate polymerized with an
anionic sur- factant system 40.3% Ammonium Chloride catalyst 0.4%
Anti-foaming agent 0.4% Zirconium Sulfate 0.6% Water 57.9 Blue
Pigment 0.4% ______________________________________
In formulating the resin, the pH is brought to about 7 before the
zirconium sulfate is added. The pH of the final formulated resin
dispersion is about 2.5.
The rayon web is passed through a dilute solution of ammonium
hydroxide in a mangle and the binder printed onto the wet,
ammoniacal web. The binder coagulates instantly, fixing the resin
in place with minimal lateral spread. The printed web is dried and
cured. The resultant fabric weighs about 250 grains per square
yard.
A swatch of the resultant fabric is stained to accurately determine
the location of the binder stripes. The binder stripe has a width
of from about 0.032 inch to 0.036 inch. The softness of the fabric
is measured with a Thwing-Albert Handle-O-Meter as about 821/4
units and the cross tensile strength of 8 piles of the fabric each
1 inch wide is 2.5 pounds.
EXAMPLE III
A fabric made as described in conjunction with Example II is made
with the following differences:
(1) no zirconium sulfate is used in the resin formulation,
(2) the web is not treated with ammonium hydroxide, and
(3) 4 lines per inch instead of 6 lines per inch are used in the
print-bonding pattern.
A swatch of the resultant fabric is stained to determine binder
stripe width which is about 0.156 inch to 0.175 inch. The softness
of the fabric is measured with a Thwing-Albert Handle-O-Meter as
about 831/2 units and the cross tensile strength of 8 plies of the
fabric each 1 inch wide is 1.8 pounds.
EXAMPLE IV
Four different fabrics are made using similar base webs of 100%
rayon fibers, 11/2 denier and 11/2 inch in length. Each fabric is
print bonded with a self cross-linking acrylic resin of polyethyl
acrylate polymerized with a non-ionic surfactant system. Two of the
fabrics are bonded in a 6 line per inch pattern described in
Example II and the other two fabrics are bonded with a similar
pattern having only 4 lines per inch. In bonding one 6 line per
inch fabric and one 4 line per inch fabric, about 0.2% by weight of
the resin of zirconium sulfate is added to the resin emulsion and
the web is treated with dilute ammonium hydroxide immediately prior
to printing it with the resin emulsion. In the other 6 line per
inch fabric and 4 line per inch fabric the zirconium sulfate and
ammonium hydroxide treatment are omitted.
Each of the resultant fabrics is tested for tenacity in the machine
and cross-directions and for stiffness in the machine and
cross-directions. The tenacity is determined by finding the force
required to break the fabric divided by the weight of the fabric.
The stiffness is determined by measuring the force required to flex
the fabric, i.e., the flexural resistance.
The following table gives the comparative results of the four
different fabrics tested:
TABLE
__________________________________________________________________________
Zirconium Sulfate & Tenacity Stiffness Ammonium Print Weight
(pounds/in/100 grains) (mg. force) Sample Hydroxide Pattern
(grains/ Machine Cross- Machine Cross- No. Treatment (lines/inch)
sq.yd.) Direction Direction Direction Direction
__________________________________________________________________________
4a No 4 670 .58 .052 30 2 4b Yes 4 580 .71 .074 7 1.1 4c No 6 720
.60 .079 32 3 4d Yes 6 610 .74 .081 9 0.7
__________________________________________________________________________
As may be readily seen from this table, the addition of zirconium
sulfate and the ammonium hydroxide treatment produces fabrics with
higher tenacity in both the machine and cross-directions as well as
fabrics which are not as stiff.
EXAMPLE V
A carded fiber web of 100% rayon fibers, 11/2 denier and 1 9/16
inch staple length is print-bonded by the rotogravure process using
an engraved roll having 6 horizontal wavy lines per inch. The width
of each line on the roll is 0.024 inch. The resin composition (pH
about 4.3) used for the print-bonding is:
(1) 1000 lbs. of a 50% solids dispersion of HA-8 (Rohm & Haas),
a self cross-linking acrylic polymer, predominantly polyethyl
acrylate, polymerized with a non-ionic surfactant system; and
(2) 8.8 lbs. of a solution (40% solids) of 9 parts zirconium
acetate and 1 part zirconium sulfate.
The carded fiber web is pre-treated and wet with 200% by weight of
the fibers of a dilute 0.1% ammonium hydroxide solution whereby it
is given a pH of about 10.
The print-bonding of the carded fiber web is otherwise conventional
and follows standard plant manufacturing processing.
The acid binder dispersion (pH about 4.3) becomes basic, coagulates
and precipitates substantially instantly upon contact with the
alkaline ammonia-wet web (pH about 10) and controllably "freezes"
the binder in place with a minimum of migration. The binder
penetrates very uniformly, substantially completely through the wet
web, which is further processed, dried and cured as usual. The
width of the binder stripe in the final product is about 0.056 inch
which represents a controlled total migration value of only about
133%. The surface coverage of the binder is about 33.6%. The final
weight of the bonded nonwoven fabric is 650 grains per square yard.
The total binder content is 21% or about 136 grains per square
yard. The concentration of binder in the binder area is about 63%
based on the weight of the fibers therein. The histogram for the
concentration of binder in the binder area is shown in FIG. 8. This
histogram is obtained by employing the optical reflectance
principle wherein the incident light having a predetermined
intensity is directed onto the surface of the bonded nonwoven
fabric and reflected therefrom. The intensity of the reflected
light is then determined, from which the "Optical Density" and the
width of the binder stripe can be measured and the relative
concentration of resin binder across the binder width can be
evaluated.
Reference to the histogram in FIG. 8 reveals that the slopes of the
curves are in the range of from 83.degree. to 85.degree.. The left
hand slope which is believed to be the leading edge of the bond is
particularly steep and rises from a zero binder concentration to a
maximum binder concentration and peak "Optical Density" of 0.74
within a lateral length of only about 0.6 mm. or 0.024 inch. The
right hand slope which is believed to be the trailing edge of the
bond is slightly less steep and rises from a zero binder
concentration to a maximum binder concentration and peak "Optical
Density" of 0.74 in about 0.8 mm. or 0.032 inch. The optical
density at one side of the bonded area (left hand side of
"INVENTION BINDER" curve in FIG. 8) increases from about 0 to a
value of at least 0.6 in moving a distance of less than about 1 mm.
from the unbonded area directly into said bonded area; thereafter
the optical density of the bonded area remains at or above a value
of at least about 0.6 until it decreases substantially to 0 in
moving a distance of less than about 1 mm. from said bonded area
directly into the next unbonded area of the fabric (right hand side
of "INVENTION BINDER" curve in FIG. 8).
The bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience. It
undergoes five standard home launderings with no appreciable damage
or change in appearance.
EXAMPLE V(a)
The procedures of Example V are followed substantially as set forth
therein except that the HA-8 self cross-linking acrylic polymer is
replaced by polyvinyl acetate. No zirconium acetate or zirconium
sulfate solution is used. All other conditions remain the same.
Print bonding is conventional and follows standard plant
manufacturing processing. Coagulation and precipitation of the
binder is not very rapid. Processing, drying and curing are
conventional. The width of the binder stripe in the final product
is about 0.190 inch which represents a total uncontrolled migration
of about 690%. The surface coverage of the binder is about 100% due
to the large amount of feathering. The total binder content is
about 21%. The average concentration of binder in the binder area
is only about 21%, based on the weight of the fibers therein, due
to the loss of binder which migrates into the feathered areas. The
product is stiff and not soft and does not possess a desirable
textile-like softness, drape or hand.
The histogram developed from an analysis of the resulting product
is shown as a dot-dash curve in FIG. 8. It is to be observed that
the peak optical density is about 0.35 whereas the peak optical
density for the invention binder in FIG. 8 is 0.74. The slope of
the curves are about 42.degree. and 41.degree. and rise very slowly
from substantially zero binder concentration to substantially
maximum binder concentration in relatively long distances of 2 mm.
(0.08 inch) and 2.1 mm. (0.084 inch).
EXAMPLE V(b)
The procedures of Example V are followed substantially as set forth
therein except that the HA-8 self cross-linking acrylic polymer is
replaced by polyvinyl chloride. No zirconium acetate or zirconium
sulfate solution is used. All other conditions remain the same.
Print bonding is conventional and follows standard plant
manufacturing processing. Coagulation and precipitation of the
binder is not very rapid. Processing, drying and curing are
conventional. The width of the binder stripe in the final product
is about 0.166 inch which represents a total uncontrolled migration
of about 590%. The surface coverage of the binder is almost 100%
due to the migration of binder into the feathered areas. The total
binder content is about 21%. The average concentration of binder in
the binder area is about 21%, based on the weight of the fibers
therein, due to the loss of binder which migrates into the
feathered areas. The product is not soft and does not possess a
desirable drape or hand.
The histogram developed from an analysis of the resulting product
is shown as a dash curve in FIG. 8. It is to be observed that the
peak optical density is about 0.37 whereas the peak optical density
for the invention binder in FIG. 8 is 0.74. The slope of the curves
are about 48.degree. and 46.degree. and very slowly rise from
substantially zero binder concentration to substantially maximum
binder concentration in relatively long distances of 1.8 mm. (0.072
inch) and 2 mm. (0.08 inch).
EXAMPLES VI & VII
A card web of 100% rayon fibers, 11/2 denier and 1 9/16 inch staple
length, is print bonded by the rotogravure process using an
engraved roll having 4 horizontal wavy lines per inch. The width of
each line on the roll is 0.024 inch. The resin composition for
Example VI is identical to that set forth in Example V. The resin
composition for Example VII, however, omits the zirconium salts and
thus does not follow the principles of the present invention.
The card web is pre-treated and wet with 165% by weight of the
fibers of a dilute ammonium hydroxide solution (0.07% NH.sub.3) and
has a pH close to about 10.
The print-bonding of the card web is otherwise conventional and
follows standard plant manufacturing processing.
The acid binder dispersion (pH about 4.3) coagulates and
precipitates when applied to the alkaline ammonia-wet web (pH about
10).
In the case of Example VI containing the zirconium salts, the
coagulation and precipitation is extremely rapid. The nonwoven
fabric is then treated, processed, dried and cured.
The width of the binder line in the final product is about 0.072
inch which represents a controlled total migration of about 200%.
The binder content in the web, determined by chemical analysis, is
about 14.6%. The weight of the bonded nonwoven fabric is about 650
grains per square yard. The weight of the binder is 95 grams per
square yard. The binder surface coverage is about 28.8%. The
concentration of binder in the binder area is about 51%, based on
the weight of the fibers therein.
In the case of Example VII where there are no zirconium salts, the
migration is uncontrolled and is much greater. The binder line
spreads to about 0.175 inch which represents a migration of about
630%. The binder surface coverage is 70% of the nonwoven fabric.
The binder content in the web, determined by chemical analysis, is
about 14.7% and the average concentration of binder in the binder
area is about 20.8%.
The bonded nonwoven fabric of Example VI has excellent strength,
excellent softness, drape and hand and excellent cross-resilience.
The bonded nonwoven fabric of Example VII neither has excellent
strength, nor excellent softness, drape and hand nor excellent
cross-resilience.
The graphs or histograms of FIG. 9 shows the difference in binder
concentration and surface coverages of Examples VI and VII.
The slopes of the curves for Example VI are approximately
75.degree. and 83.degree. for the trailing and leading edges of the
bond, whereas the slopes for the curves for Example VII are only
about 46.degree. and 51.degree.. The curves for Example VI rapidly
climb from zero to substantially maximum binder concentrations and
peak optical density of 0.90 in about 1 mm. and 0.6 mm. (0.040 inch
and 0.024 inch). The optical density at one side of a bonded area
of the fabric of Example VI (left hand side of "INVENTION BINDER"
curve in FIG. 9) increases from about 0 to a value of at least 0.6
in moving a distance of less than about 1 mm. from the unbonded
area directly into said bonded area; thereafter the optical density
of the bonded area remains at or above a value of at least about
0.6 until it decreases substantially to 0 in moving a distance of
less than about 1 mm. from said bonded area directly into the next
unbonded area of the fabric (right hand side of "INVENTION BINDER"
curve in FIG. 9). In fact, the optical density at the left hand
side of the INVENTION BINDER curve of FIG. 9 increases from
substantially 0 to about 0.6 in moving a distance of approximately
0.4 mm. from the unbonded area directly into the bonded area; and
the optical density at the right hand side of the same curve
decreases from about 0.6 to substantially 0 in moving a distance of
less than approximately 0.4 mm. directly from the bonded area into
the next unbonded area of the fabric. In Example VII the longer
distances required to reach peak optical density of 0.44 are each
in excess of 2.5 mm. (0.100 inch).
EXAMPLE VIII
A fibrous web weighing 590 grains per square yard and comprising
100% rayon fibers 11/2 denier and 11/2 inches in length is
intermittently print-bonded by the rotogravure process using an
engraved roll having 4 horizontal wavy lines per inch, the width of
each line, as measured on the engraved roll, being 0.024 inch.
The composition by weight of the resin binder formulation used for
the print-bonding is:
______________________________________ Self cross-linking acrylic
polymer, predominantly polyethyl acrylate, polymerized with a
non-ionic surfactant 46.0% Anti-foaming agent 0.4% Zirconium
acetate-zirconium sulfate mixture (9:1 ratio) 0.5% Water 53.1%
______________________________________
The resin dispersion, as received, possesses a pH of 3. The final
resin dispersion formulation has a pH of 4. The rayon web is passed
through a dilute solution of ammonium hyroxide in a mangle, taking
up ammonium hydroxide and becoming alkaline as a result. The acidic
binder dispersion is then printed onto the wet, ammoniacal web. The
pH of the binder dispersion is promptly increased to greater than 7
and the binder coagulates instantly, fixing the resin in place with
minimal lateral spreading or diffusion. The printed web is dried
and cured. The resulting bonded fabric weighs 690 grains per square
yard. The bonded fabric thus contains 14.6% by weight of binder,
based on the total weight of the bonded fabric.
A swatch of the resultant bonded fabric is stained to determine
accurately the location of the binder stripes. The Optical Density
method is used to determine the widths and relative concentrations
of binder. The binder width in the finished fabric is 0.038 inch,
which represents an increase due to migration of 58%. The surface
coverage is 15.2%.
The bonded fabric is strong and is also very soft, due primarily to
the fact that the binder is concentrated so heavily in the binder
area and has not spread or migrated very much. There is 96% by
weight of binder in the binder areas, based on the weight of the
fibers in the binder areas.
EXAMPLE IX
The procedures of Example VIII are followed substantially as set
forth therein except that the zirconium acetate-zirconium sulfate
is omitted from the binder formulation.
The resultant bonded fabric is weaker than the bonded fabric of
Example VIII and is not as soft. It is crisper, harsher and less
textile-like. The final width of the binder stripe is 0.107 inch,
thus indicating a lateral spread or migration of 346%. The surface
coverage is 42.8%. There is, on the average, 34.2% by weight of
binder in the binder areas, based on the weight of the fibers in
the binder areas.
EXAMPLE X
Approximately 7 grams of the di-calcium salt of
ethylenediaminetetraacetic acid is directly added with stirring to
approximately 1400 grams of a polyvinyl acetate emulsion of about
55% solids. The emulsion contains approximately 720 grams of vinyl
acetate polymer stabilized with about 35 grams of dodecyl benzene
sulfonate with the remainder water. Sufficient ammonia is added to
the emulsion to bring the pH to 8.
A fibrous web of 100% ray fibers, 11/2 denier and 11/2 inch in
length is impregnated with a 0.5% aqueous solution of acetic acid.
The above described resin emulsion is printed on the treated web in
a pattern of four horizontal wavy lines per inch. At the moment of
printing, the alkaline resin emulsion meets the acid web,
liberating calcium ions and destroying the effectiveness of the
anionic surfactant (dodecyl benzene sulfonate). The resin particles
are immediately precipitated and not allowed to migrate
excessively.
EXAMPLE XI
A fibrous web of 100% rayon fibers, 11/2 denier and 11/2 inch in
length, weighing 500 grains per square yard, is impregnated to 100%
by weight pick-up with a 0.2% aqueous solution of a salt of a
complex polyamine. An example of such a salt is sold by the Rohm
& Haas Company under the Trademark LUFAX 295.
A resin dispersion containing 40% by weight of a self cross-linking
acrylic polymer which is predominantly ethyl acrylate, 0.4% of
Ammonium Chloride catalyst, 0.4% of an antifoaming agent, with the
remainder water is printed on the impregnated web in a pattern of
six horizontal wavy lines per inch. The printing of the resin
binder pattern on the fibrous web takes place while the fibrous web
is still wet with the polyamine solution.
The width of each line printed is about 0.018 inch as measured on
the engraved roll. The amount of resin solids applied is
approximately 20% by weight of the web.
The printed fabric is dried at 270.degree. F. for 30 seconds in
contact with heated metal rollers. The resultant fabric weighs 600
grains per square yard. The width of the binder stripe in the
resultant fabric is approximately 0.035 inch and extends completely
through the fabric from the top surface to the bottom surface.
EXAMPLE XII
A fabric made as described in conjunction with Example XI is made
with the exception that the salt of the complex polyamine is
omitted from the initial impregnating aqueous solution. The width
of the binder stripe in the resultant fabric is approximately 0.16
inch or almost 5 times as wide as the width of the binder stripe of
the fabric of Example XI.
EXAMPLE XIII
The procedures of Example XI are followed substantially as set
forth therein except that the fibrous web is dried after its
impregnation with the polyamine solution. The resin binder
dispersion is then printed with a similar 6-line pattern on the
dried fibrous web. Study of the bonded fabric, after final drying,
reveals that the resin binder is primarily on the top surface of
the fabric and that it has not penetrated into the fabric to any
significant extent. As a result, the fabric is substantially
unbonded on its bottom surface. Such non-uniform bonding is
undesirable and the product is unsatisfactory for use in the
nonwoven fabric industry.
EXAMPLE XIV
The procedures set forth in Example XI are carried out
substantially as set forth therein except that 0.2% of the
polyethylene imine having a molecular weight of about 20,000 is
substituted for the 0.2% of a salt of a complex polyamine. The
results are comparable to those of Example XI. The resin bonding
extends through the fibrous web from the top surface thereof to the
bottom surface and the lateral migration of the binder is
minimal.
EXAMPLE XV
The procedures set forth in Example XI are carried out
substantially as set forth therein except that 0.5% of a cationic
starch containing complex amine groups is substituted for the 0.2%
of a salt of a complex polyamine. Results comparable to those of
Example XI are obtained. The resin bonding extends completely
through the fibrous web from the top surface thereof to the bottom
surface. The lateral migration of the binder is minimal.
EXAMPLE XVI
The procedures of Example XI are followed substantially as set
forth therein except that RETEN 210 (Hercules Chemical Co.), a
strongly cationic, water-soluble, synthetic, complex polyamine
having a very high molecular weight of at least about one million
is used. After impregnation of the fibrous web with the polyamine
and while the fibrous web is still wet, the resin dispersion is
printed thereon. The results are satisfactory and are comparable to
the results obtained in Example XI. The resin bonding extends
completely through the fibrous web from the top surface to the
bottom. The lateral migration of the binder is minimal.
EXAMPLE XVII
The procedures of Example XI are followed substantially as set
forth therein with the exception that the resin dispersion contains
approximately 45% by weight of a polyvinyl acetate-N-methylol
acrylamide copolymer. The resin binder penetrates through the
fabric very rapidly and bonds it satisfactorily from the top
surface to the bottom surface. The lateral migration of the binder
is minimal.
EXAMPLE XVIII
The procedures of Example XI are followed substantially as set
forth therein except that the resin used is a polyvinyl
acetate-ethyl acrylate copolymer. The results are comparable to
those obtained in Example XI. The resin binder extends completely
through the fibrous web and bonds it satisfactorily from the top
surface to the bottom surface. The lateral migration of the binder
is minimal.
EXAMPLE XIX
The procedures of Example XI are followed substantially as set
forth therein except that the resin used is a methyl
methacrylate-ethyl acrylate copolymer. The results are comparable
to those obtained in Example XI. The resin binder extends
completely through the fibrous web and bonds it satisfactorily from
the top surface to the bottom surface. The lateral migration of the
binder is minimal.
EXAMPLE XX
The procedures of Example XI are followed substantially as set
forth therein except that the resin used is a methyl
methacrylate-ethyl hexyl acrylate copolymer. The results are
comparable to those obtained in Example XI. The resin binder
extends completely through the fibrous web and bonds it
satisfactorily from the top surface to the bottom surface. The
lateral migration of the binder is minimal.
EXAMPLE XXI
The procedures of Example XI are followed substantially as set
forth therein except that the resin used is a butyl acrylate-methyl
methacrylate copolymer. The results are comparable to those
obtained in Example XI. The resin binder extends completely through
the fibrous web and bonds it satisfactorily from the top surface to
the bottom surface. The lateral migration of the binder is
minimal.
EXAMPLE XXII
A fibrous card web weighing about 570 grains per square yard and
comprising 100% rayon fibers 11/2 denier and 11/2 inches in length
is intermittently print-bonded by the rotogravure process using an
engraved roll having 6 horizontal wavy lines per inch. The width of
each line as measured on the engraved roll is 0.024 inch.
The composition by weight of the resin binder formulation used for
the intermittent print-bonding is:
(1) 100 lbs. of a 50% solids latex of GAF 243 terpolymer of
butadiene (46%), styrene (51%), and .alpha.,.beta. -unsaturated
carboxylic acid (2%).
(2) 40 lbs. of distilled water.
(3) 10 lbs. of a 10% solution of a thickening agent, Acrysol 51, a
copolymer of acrylic acid.
(4) 150 grams "Pluronic L101" Polyol ethylene oxide condensates of
hydrophobic bases of propylene oxide and propylene glycol nonionic
surfactant.
(5) 900 grams of a 48% solution of zinc tetrammine sulfate metal
coordination complex containing 17% zinc oxide equivalent or 1 lb.
zinc tetrammine sulfate (actual).
The resin dispersion, as prepared, has a pH of 9. The fibrous web
is pretreated and wet with 165% of its weight of acetic acid (0.1%)
to bring it to a pH below 7 and wherein it possesses sufficient
acidity to more than neutralize the alkaline pH of the resin
dispersion which is to be applied thereto.
The alkaline binder dispersion is then printed onto the wet, acetic
acid treated fibrous web in the form of a 6-line intermittent print
pattern. The pH of the binder dispersion is immediately decreased
to less than 7 and the binder coagulates and precipitates
instantly, fixing the resin in place on the web with controlled
minimal lateral spreading or diffusion. The printed web is then
processed, dried and cured in conventional fashion. The resulting
bonded nonwoven fabric weighs 690 grains per square yard and
contains 17.4% by weight of binder based on the total weight of the
bonded nonwoven fabric.
The binder line possesses a width of 0.066 in the final dried
fabric which represents a controlled total migration of about 190%.
The surface coverage of the binder is 26.4% of the nonwoven fabric
and the concentration of binder in the binder area is 66%, based on
the weight of the fibers therein.
The bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
The histogram of FIG. 10 graphically depicts the advantages of the
present invention. The slopes of the curves are 78.degree.
(presumably the trailing bond edge) and 83.degree. (presumably the
leading edge of the bond) and it requires only 0.6 mm. and 0.8 mm.
(0.024 inch and 0.032 inch) to increase from zero to substantially
maximum concentration of binder in the binder area at 0.80 Optical
Density and 0.16 Optical Transparency. The optical density at one
side of a bonded area of the fabric of Example XXII (left hand side
of "INVENTION BINDER" curve in FIG. 10) increases from about 0 to a
value of at least 0.6 in moving a distance of less than about 1 mm.
from the unbonded area directly into said bonded area; thereafter
the optical density of the bonded area remains at or above a value
of at least about 0.6 until it decreases substantially to 0 in
moving a distance of less than about 1 mm. from said bonded area
directly into the next unbonded area of the fabric (right hand side
of "INVENTION BINDER" curve in FIG. 10). In fact, the optical
density at the left hand side of the INVENTION BINDER curve of FIG.
10 increases from substantially 0 to about 0.6 in moving a distance
of approximately 0.5 mm. from the unbonded area directly into the
bonded area; and the optical density at the right hand side of the
same curve decreases from about 0.6 to substantially 0 in moving a
distance of approximately 0.3 mm. directly from the bonded area
into the next unbonded area of the fabric.
EXAMPLE XXII(a)
The procedures of Example XXII are followed substantially as set
forth therein except that the carboxylated butadiene styrene
polymer is replaced by polyvinyl acetate. No zinc tetrammine
sulfate solution is used. All other conditions remain the same.
Print-bonding is conventional and follows standard plant
manufacturing processing. Coagulation and precipitation of the
binder is not very rapid. Processing, drying and curing are
conventional. The width of the binder stripe in the final product
is about 0.170 inch which represents a total migration of about
610% due to the migration of binder into the feathered areas. The
surface coverage of the binder is about 100%, again, due to the
migration of binder into the feathered areas. The total binder
content is about 17.4%. The average concentration of binder in the
binder area is about 17.4%, based on the weight of the fibers
therein. The product is stiff and not soft and does not possess a
desirable drape or hand.
The histogram developed from an analysis of the resulting product
is shown as a dash curve in FIG. 10. It is to be observed that the
peak Optical Density is about 0.36 whereas the peak Optical Density
for the invention binder in FIG. 10 is 0.80. The slope of the
curves are about 46.degree. and 50.degree. and rise from
substantially zero binder concentration to substantially maximum
binder concentration in relatively long distances of 1.8 mm. (0.72
inch) and 2.0 mm. (0.80 inch).
EXAMPLE XXIII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the coordination complex
compound is zinc tetrammine carbonate rather than zinc tetrammine
sulfate. The results are generally comparable and the bonded
nonwoven fabric is generally comparable to the bonded nonwoven
fabric obtained in Example XXII.
EXAMPLE XXIV
The procedures of Example XXII are followed substantially as set
forth therein except that the zinc tetrammine sulfate is replaced
by ammonium zirconyl carbonate,
The results are generally comparable and the resulting bonded
nonwoven fabric possesses properties and characteristics generally
similar to that obtained in the bonded nonwoven fabric of Example
XXII.
EXAMPLE XXV
The procedures of Example XXII are followed substantially as set
forth therein exept that the zinc tetrammine sulfate is replaced by
sodium tetrahydroxo zincate. The results are generally comparable
and the resulting bonded nonwoven fabric possesses properties and
characteristics generally similar to those obtained in the bonded
nonwoven fabric of Example XXII.
EXAMPLE XXVI
The procedures of Example XXII are followed substantially as set
forth therein except that the zinc tetrammine sulfate is replaced
by sodium tetrahydroxo aluminate. The results are generally
comparable and the resulting bonded nonwoven fabric possesses
properties and characteristics generally similar to those obtained
in the bonded nonwoven fabric of Example XXII.
EXAMPLE XXVII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the percentage of the
.alpha.,.beta. -unsaturated carboxylic acid is decreased to 1% and
the percentages of the butadiene and sytrene are proportionately
increased.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXVIII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the percentage of the
.alpha.,.beta. -unsaturated carboxylic acid is increased to 4% and
the percentages of the butadiene and styrene are proportionately
decreased.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent softness, drape and
hand, and excellent cross-resilience.
EXAMPLE XXIX
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the percentage of the
.alpha.,.beta. -unsaturated carboxylic acid is increased to 6% and
the percentages of the butadiene and styrene are proportionately
decreased.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXX
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the quantity of the
coordination complex is decreased from 900 grams zinc tetrammine
sulfate to 450 grams or 1/2 lb. zinc tetrammine sulfate
(actual).
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXXI
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the quantity of the
coordination complex is increased from 900 grams zinc tetrammine
sulfate to 1350 grams or 11/2 lbs. zinc tetrammine sulfate
(actual).
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXXII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the butadiene-styrene
.alpha.,.beta. -unsaturated acid terpolymer is replaced by Goodrich
2600X83 copolymer of an acrylic resin with an .alpha.,.beta.
-unsaturated carboxylic acid. An anionic surfactant is used in this
formulation.
The carboxylated copolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXXIII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the terpolymer used therein
is replaced by National Starch P306-3, a copolymer of 97% acrylic
monomer and 3% acrylic acid with an anionic surfactant system.
The carboxylated copolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXXIV
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the terpolymer used therein
is replaced by a terpolymer of ethylene, vinyl acetate, and an
.alpha.,.beta. -unsaturated carboxylic acid.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and migration is held to a minimum.
Conventional processing, drying, and curing are employed. The
resulting bonded nonwoven fabric has excellent strength, excellent
softness, drape and hand, and excellent cross-resilience.
EXAMPLE XXXV
The procedures of Example XXII are carried out substantially as set
forth therein except that the GAF 243 carboxylated
butadiene-styrene terpolymer is replaced by an equivalent amount of
a terpolymer of 51% butadiene, 48% styrene, and 2% acrylic
acid.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and the total migration is held to
a minimum. Conventional processing, drying, and curing are
employed. The resulting bonded nonwoven fabric is generally
comparable to the bonded nonwoven fabric obtained in Example
XXII.
EXAMPLE XXXVI
The procedures of Example XXII are carried out substantially as set
forth therein except that the GAF 243 carboxylated
butadiene-styrene terpolymer is replaced by an equivalent amount of
a terpolymer of 51% butadiene, 48% styrene, and 2% methacrylic
acid.
The carboxylated terpolymer resin binder dispersion coagulates and
precipitates substantially immediately upon being printed on the
acetic acid treated fibrous web and the total migration is held to
a minimum. Conventional processing, drying, and curing are
employed. The resulting bonded nonwoven fabric is generally
comparable to the bonded nonwoven fabric obtained in Example
XXII.
EXAMPLE XXXVII
The procedures of Example XXXVI are followed substantially as set
forth therein with the exception that the resin formulation
comprises 46% butadiene, 51% styrene, and 2% itaconic acid, plus a
sodium salt of a phosphate ester as an anionic surfactant mixture.
Coagulation and precipitation take place satisfactorily. Total
migration is controlled and held to a minimum. The resulting bonded
nonwoven fabric is generally comparable to the bonded nonwoven
fabric obtained in Example XXXVI.
EXAMPLE XXXVIII
The procedures of Example XXII are followed substantially as set
forth therein with the exception that the rayon fibers are replaced
by bleached cotton fibers.
The results are comparable and the resulting nonwoven fabric has
excellent strength, excellent softness, drape and hand, and
excellent cross-resilience.
EXAMPLE XXXIX
The procedures of Example XXII are followed substantially as set
forth therein with the exception that water-insoluble polyvinyl
alcohol fibers (Kurashiki - 2.5 denier) are used instead of the
rayon fibers.
The results are comparable and the properties and characteristics
of the resulting nonwoven fabric are excellent, particularly with
regard to strength, both wet and dry.
Having now described the invention in specific detail and
exemplified the manner in which it may be carried into practice, it
will be readily apparent to those skilled in the art that
innumerable variations, applications, modifications, and extensions
of the basic principles involved may be made without departing from
its spirit and scope.
* * * * *